Add PDF translation API, utilities, docs, and config

Introduces core backend and frontend infrastructure for a PDF translation interface. Adds API endpoints for translation, PDF testing, and AI provider testing; implements PDF text extraction, cost tracking, and pricing logic in the lib directory; adds reusable UI components; and provides comprehensive documentation (SDD, environment setup, Claude instructions). Updates Tailwind and global styles, and includes a sample test PDF and configuration files.

app/api/test-api/route.ts

@@ -0,0 +1,67 @@
+import { type NextRequest, NextResponse } from "next/server"
+import { createOpenAI } from "@ai-sdk/openai"
+import { openai } from "@ai-sdk/openai"
+import { generateText } from "ai"
+
+export async function POST(request: NextRequest) {
+  try {
+    const { provider, apiKey } = await request.json()
+
+    if (!provider || !apiKey) {
+      return NextResponse.json({ error: "缺少必要參數" }, { status: 400 })
+    }
+
+    let model
+    let modelName: string
+
+    if (provider === "openai") {
+      // Test OpenAI
+      modelName = "gpt-4o-mini"
+      model = openai(modelName, { apiKey })
+    } else {
+      // Test DeepSeek
+      modelName = "deepseek-chat"
+      const deepseek = createOpenAI({
+        apiKey: apiKey,
+        baseURL: "https://api.deepseek.com",
+      })
+      model = deepseek(modelName)
+    }
+
+    // Test with a simple prompt
+    const { text } = await generateText({
+      model: model,
+      prompt: "Hello, this is a test. Please respond with 'API connection successful!'",
+      maxTokens: 50,
+      temperature: 0,
+    })
+
+    return NextResponse.json({ 
+      success: true, 
+      message: "API 連接成功！",
+      provider,
+      model: modelName,
+      testResponse: text
+    })
+
+  } catch (error: any) {
+    console.error("API Test Error:", error)
+    
+    let errorMessage = "API 測試失敗"
+    
+    if (error.message?.includes("API key")) {
+      errorMessage = "API 金鑰無效或已過期"
+    } else if (error.message?.includes("rate limit")) {
+      errorMessage = "API 請求次數超過限制"
+    } else if (error.message?.includes("quota")) {
+      errorMessage = "API 配額已用完"
+    } else if (error.message?.includes("Not Found")) {
+      errorMessage = "API 端點錯誤或模型不存在"
+    }
+
+    return NextResponse.json({ 
+      error: errorMessage,
+      details: error.message 
+    }, { status: 400 })
+  }
+}