feat: Add multi-LLM provider support with DeepSeek integration

Major Features:
- ✨ Multi-LLM provider support (DeepSeek, Ollama, OpenAI, Custom)
- 🤖 Admin panel LLM configuration management UI
- 🔄 Dynamic provider switching without restart
- 🧪 Built-in API connection testing
- 🔒 Secure API key management

Backend Changes:
- Add routes/llmConfig.js: Complete LLM config CRUD API
- Update routes/analyze.js: Use database LLM configuration
- Update server.js: Add LLM config routes
- Add scripts/add-deepseek-config.js: DeepSeek setup script

Frontend Changes:
- Update src/pages/AdminPage.jsx: Add LLM Config tab + modal
- Update src/services/api.js: Add LLM config API methods
- Provider presets for DeepSeek, Ollama, OpenAI
- Test connection feature in config modal

Configuration:
- Update .env.example: Add DeepSeek API configuration
- Update package.json: Add llm:add-deepseek script

Documentation:
- Add docs/LLM_CONFIGURATION_GUIDE.md: Complete guide
- Add DEEPSEEK_INTEGRATION.md: Integration summary
- Quick setup instructions for DeepSeek

API Endpoints:
- GET /api/llm-config: List all configurations
- GET /api/llm-config/active: Get active configuration
- POST /api/llm-config: Create configuration
- PUT /api/llm-config/🆔 Update configuration
- PUT /api/llm-config/:id/activate: Activate configuration
- DELETE /api/llm-config/🆔 Delete configuration
- POST /api/llm-config/test: Test API connection

Database:
- Uses existing llm_configs table
- Only one config active at a time
- Fallback to Ollama if no database config

Security:
- Admin-only access to LLM configuration
- API keys never returned in GET requests
- Audit logging for all config changes
- Cannot delete active configuration

DeepSeek Model:
- Model: deepseek-chat
- High-quality 5 Why analysis
- Excellent Chinese language support
- Cost-effective pricing

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/AdminPage.jsx

@@ -28,6 +28,7 @@ export default function AdminPage() {
             { id: 'dashboard', name: '總覽', icon: '📊' },
             { id: 'users', name: '使用者管理', icon: '👥' },
             { id: 'analyses', name: '分析記錄', icon: '📝' },
+            { id: 'llm', name: 'LLM 配置', icon: '🤖' },
             { id: 'audit', name: '稽核日誌', icon: '🔍' },
           ].map(tab => (
             <button
@@ -50,6 +51,7 @@ export default function AdminPage() {
       {activeTab === 'dashboard' && <DashboardTab />}
       {activeTab === 'users' && <UsersTab />}
       {activeTab === 'analyses' && <AnalysesTab />}
+      {activeTab === 'llm' && <LLMConfigTab />}
       {activeTab === 'audit' && <AuditTab />}
     </div>
   );
@@ -366,6 +368,368 @@ function AuditTab() {
   );
 }
 
+// LLM Config Tab Component
+function LLMConfigTab() {
+  const [configs, setConfigs] = useState([]);
+  const [loading, setLoading] = useState(true);
+  const [showModal, setShowModal] = useState(false);
+  const [editingConfig, setEditingConfig] = useState(null);
+
+  useEffect(() => {
+    loadConfigs();
+  }, []);
+
+  const loadConfigs = async () => {
+    try {
+      const response = await api.getLLMConfigs();
+      if (response.success) {
+        setConfigs(response.data);
+      }
+    } catch (err) {
+      console.error(err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  const activateConfig = async (id) => {
+    try {
+      await api.activateLLMConfig(id);
+      loadConfigs();
+    } catch (err) {
+      alert('啟用失敗: ' + err.message);
+    }
+  };
+
+  const deleteConfig = async (id) => {
+    if (!confirm('確定要刪除此 LLM 配置嗎？')) return;
+
+    try {
+      await api.deleteLLMConfig(id);
+      loadConfigs();
+    } catch (err) {
+      alert('刪除失敗: ' + err.message);
+    }
+  };
+
+  if (loading) return <div className="text-center py-12">載入中...</div>;
+
+  return (
+    <div>
+      <div className="mb-4 flex justify-between items-center">
+        <div>
+          <h3 className="text-lg font-semibold">LLM 配置管理</h3>
+          <p className="text-sm text-gray-600 mt-1">配置 AI 模型 (DeepSeek, Ollama 等)</p>
+        </div>
+        <button
+          onClick={() => {
+            setEditingConfig(null);
+            setShowModal(true);
+          }}
+          className="px-4 py-2 bg-indigo-600 text-white rounded-lg hover:bg-indigo-700"
+        >
+          ➕ 新增配置
+        </button>
+      </div>
+
+      <div className="bg-white rounded-lg shadow-sm border border-gray-200 overflow-hidden">
+        <table className="min-w-full divide-y divide-gray-200">
+          <thead className="bg-gray-50">
+            <tr>
+              <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">提供商</th>
+              <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">API 端點</th>
+              <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">模型</th>
+              <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">狀態</th>
+              <th className="px-6 py-3 text-left text-xs font-medium text-gray-500 uppercase">建立時間</th>
+              <th className="px-6 py-3 text-right text-xs font-medium text-gray-500 uppercase">操作</th>
+            </tr>
+          </thead>
+          <tbody className="bg-white divide-y divide-gray-200">
+            {configs.map((config) => (
+              <tr key={config.id} className="hover:bg-gray-50">
+                <td className="px-6 py-4 whitespace-nowrap">
+                  <span className="font-medium text-gray-900">{config.provider_name}</span>
+                </td>
+                <td className="px-6 py-4 text-sm text-gray-600 max-w-xs truncate">
+                  {config.api_endpoint}
+                </td>
+                <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-900">
+                  {config.model_name}
+                </td>
+                <td className="px-6 py-4 whitespace-nowrap">
+                  {config.is_active ? (
+                    <span className="px-2 py-1 text-xs font-medium rounded-full bg-green-100 text-green-700">
+                      啟用中
+                    </span>
+                  ) : (
+                    <span className="px-2 py-1 text-xs font-medium rounded-full bg-gray-100 text-gray-700">
+                      未啟用
+                    </span>
+                  )}
+                </td>
+                <td className="px-6 py-4 whitespace-nowrap text-sm text-gray-500">
+                  {new Date(config.created_at).toLocaleString('zh-TW')}
+                </td>
+                <td className="px-6 py-4 whitespace-nowrap text-right text-sm space-x-2">
+                  {!config.is_active && (
+                    <button
+                      onClick={() => activateConfig(config.id)}
+                      className="text-green-600 hover:text-green-900"
+                    >
+                      啟用
+                    </button>
+                  )}
+                  <button
+                    onClick={() => {
+                      setEditingConfig(config);
+                      setShowModal(true);
+                    }}
+                    className="text-indigo-600 hover:text-indigo-900"
+                  >
+                    編輯
+                  </button>
+                  {!config.is_active && (
+                    <button
+                      onClick={() => deleteConfig(config.id)}
+                      className="text-red-600 hover:text-red-900"
+                    >
+                      刪除
+                    </button>
+                  )}
+                </td>
+              </tr>
+            ))}
+          </tbody>
+        </table>
+      </div>
+
+      {showModal && (
+        <LLMConfigModal
+          config={editingConfig}
+          onClose={() => setShowModal(false)}
+          onSuccess={() => {
+            setShowModal(false);
+            loadConfigs();
+          }}
+        />
+      )}
+    </div>
+  );
+}
+
+// LLM Config Modal
+function LLMConfigModal({ config, onClose, onSuccess }) {
+  const [formData, setFormData] = useState({
+    provider_name: config?.provider_name || 'DeepSeek',
+    api_endpoint: config?.api_endpoint || 'https://api.deepseek.com',
+    api_key: '',
+    model_name: config?.model_name || 'deepseek-chat',
+    temperature: config?.temperature || 0.7,
+    max_tokens: config?.max_tokens || 6000,
+    timeout_seconds: config?.timeout_seconds || 120,
+  });
+  const [loading, setLoading] = useState(false);
+  const [testing, setTesting] = useState(false);
+  const [error, setError] = useState('');
+  const [testResult, setTestResult] = useState('');
+
+  const providerPresets = {
+    DeepSeek: {
+      api_endpoint: 'https://api.deepseek.com',
+      model_name: 'deepseek-chat',
+    },
+    Ollama: {
+      api_endpoint: 'https://ollama_pjapi.theaken.com',
+      model_name: 'qwen2.5:3b',
+    },
+    OpenAI: {
+      api_endpoint: 'https://api.openai.com',
+      model_name: 'gpt-4',
+    },
+  };
+
+  const handleProviderChange = (provider) => {
+    setFormData({
+      ...formData,
+      provider_name: provider,
+      ...(providerPresets[provider] || {}),
+    });
+  };
+
+  const testConnection = async () => {
+    setTesting(true);
+    setTestResult('');
+    setError('');
+
+    try {
+      const response = await api.testLLMConfig({
+        api_endpoint: formData.api_endpoint,
+        api_key: formData.api_key,
+        model_name: formData.model_name,
+      });
+      setTestResult('✅ 連線測試成功！');
+    } catch (err) {
+      setError('連線測試失敗: ' + err.message);
+    } finally {
+      setTesting(false);
+    }
+  };
+
+  const handleSubmit = async (e) => {
+    e.preventDefault();
+    setLoading(true);
+    setError('');
+
+    try {
+      if (config) {
+        await api.updateLLMConfig(config.id, formData);
+      } else {
+        await api.createLLMConfig(formData);
+      }
+      onSuccess();
+    } catch (err) {
+      setError(err.message);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center p-4 z-50">
+      <div className="bg-white rounded-lg shadow-xl max-w-2xl w-full p-6 max-h-[90vh] overflow-y-auto">
+        <h3 className="text-xl font-bold mb-4">
+          {config ? '編輯 LLM 配置' : '新增 LLM 配置'}
+        </h3>
+
+        {error && (
+          <div className="bg-red-50 border border-red-200 text-red-700 px-3 py-2 rounded mb-4 text-sm">
+            {error}
+          </div>
+        )}
+
+        {testResult && (
+          <div className="bg-green-50 border border-green-200 text-green-700 px-3 py-2 rounded mb-4 text-sm">
+            {testResult}
+          </div>
+        )}
+
+        <form onSubmit={handleSubmit} className="space-y-4">
+          <div>
+            <label className="block text-sm font-medium mb-1">提供商 *</label>
+            <select
+              value={formData.provider_name}
+              onChange={(e) => handleProviderChange(e.target.value)}
+              className="w-full px-3 py-2 border rounded-lg"
+              required
+            >
+              <option value="DeepSeek">DeepSeek</option>
+              <option value="Ollama">Ollama</option>
+              <option value="OpenAI">OpenAI</option>
+              <option value="Other">其他</option>
+            </select>
+          </div>
+
+          <div>
+            <label className="block text-sm font-medium mb-1">API 端點 *</label>
+            <input
+              type="url"
+              value={formData.api_endpoint}
+              onChange={(e) => setFormData({...formData, api_endpoint: e.target.value})}
+              className="w-full px-3 py-2 border rounded-lg"
+              placeholder="https://api.deepseek.com"
+              required
+            />
+          </div>
+
+          <div>
+            <label className="block text-sm font-medium mb-1">API Key</label>
+            <input
+              type="password"
+              value={formData.api_key}
+              onChange={(e) => setFormData({...formData, api_key: e.target.value})}
+              className="w-full px-3 py-2 border rounded-lg"
+              placeholder="選填（某些 API 需要）"
+            />
+          </div>
+
+          <div>
+            <label className="block text-sm font-medium mb-1">模型名稱 *</label>
+            <input
+              type="text"
+              value={formData.model_name}
+              onChange={(e) => setFormData({...formData, model_name: e.target.value})}
+              className="w-full px-3 py-2 border rounded-lg"
+              placeholder="deepseek-chat"
+              required
+            />
+          </div>
+
+          <div className="grid grid-cols-3 gap-4">
+            <div>
+              <label className="block text-sm font-medium mb-1">Temperature</label>
+              <input
+                type="number"
+                step="0.1"
+                min="0"
+                max="2"
+                value={formData.temperature}
+                onChange={(e) => setFormData({...formData, temperature: parseFloat(e.target.value)})}
+                className="w-full px-3 py-2 border rounded-lg"
+              />
+            </div>
+
+            <div>
+              <label className="block text-sm font-medium mb-1">Max Tokens</label>
+              <input
+                type="number"
+                value={formData.max_tokens}
+                onChange={(e) => setFormData({...formData, max_tokens: parseInt(e.target.value)})}
+                className="w-full px-3 py-2 border rounded-lg"
+              />
+            </div>
+
+            <div>
+              <label className="block text-sm font-medium mb-1">Timeout (秒)</label>
+              <input
+                type="number"
+                value={formData.timeout_seconds}
+                onChange={(e) => setFormData({...formData, timeout_seconds: parseInt(e.target.value)})}
+                className="w-full px-3 py-2 border rounded-lg"
+              />
+            </div>
+          </div>
+
+          <div className="flex space-x-3 pt-4">
+            <button
+              type="button"
+              onClick={testConnection}
+              disabled={testing}
+              className="px-4 py-2 border border-indigo-600 text-indigo-600 rounded-lg hover:bg-indigo-50 disabled:opacity-50"
+            >
+              {testing ? '測試中...' : '🔍 測試連線'}
+            </button>
+            <div className="flex-1"></div>
+            <button
+              type="button"
+              onClick={onClose}
+              className="px-4 py-2 border rounded-lg hover:bg-gray-50"
+            >
+              取消
+            </button>
+            <button
+              type="submit"
+              disabled={loading}
+              className="px-4 py-2 bg-indigo-600 text-white rounded-lg hover:bg-indigo-700 disabled:opacity-50"
+            >
+              {loading ? '儲存中...' : '儲存'}
+            </button>
+          </div>
+        </form>
+      </div>
+    </div>
+  );
+}
+
 // Create User Modal
 function CreateUserModal({ onClose, onSuccess }) {
   const [formData, setFormData] = useState({

src/services/api.js

@@ -170,6 +170,38 @@ class ApiClient {
     return this.get('/api/admin/statistics');
   }
 
+  // ============================================
+  // LLM Configuration APIs
+  // ============================================
+
+  async getLLMConfigs() {
+    return this.get('/api/llm-config');
+  }
+
+  async getActiveLLMConfig() {
+    return this.get('/api/llm-config/active');
+  }
+
+  async createLLMConfig(configData) {
+    return this.post('/api/llm-config', configData);
+  }
+
+  async updateLLMConfig(id, configData) {
+    return this.put(`/api/llm-config/${id}`, configData);
+  }
+
+  async activateLLMConfig(id) {
+    return this.put(`/api/llm-config/${id}/activate`, {});
+  }
+
+  async deleteLLMConfig(id) {
+    return this.delete(`/api/llm-config/${id}`);
+  }
+
+  async testLLMConfig(configData) {
+    return this.post('/api/llm-config/test', configData);
+  }
+
   // ============================================
   // Health Check
   // ============================================