Add Flask/Python backend server

- Create app.py with Flask server on port 5002
- Add requirements.txt with Python dependencies
- Add run_flask.bat for Windows users
- Add run_flask.sh for Linux/Mac users
- Complete Flask setup documentation
- Database integration with PyMySQL
- Full LLM API support (Gemini, DeepSeek, OpenAI, Claude)
- CORS configuration
- Error handling middleware

Features:
✅ Runs on http://127.0.0.1:5002
✅ All LLM APIs supported
✅ Database connection
✅ API proxy for CORS fix
✅ Auto setup scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

run_flask.sh

@@ -0,0 +1,54 @@
+#!/bin/bash
+
+# Flask 伺服器啟動腳本
+
+echo "========================================"
+echo "HR Performance System - Flask Server"
+echo "========================================"
+echo ""
+
+# 檢查 Python 是否安裝
+if ! command -v python3 &> /dev/null; then
+    echo "[ERROR] Python 3 is not installed"
+    echo "Please install Python 3.8 or higher"
+    exit 1
+fi
+
+# 檢查虛擬環境
+if [ ! -d "venv" ]; then
+    echo "[INFO] Creating virtual environment..."
+    python3 -m venv venv
+    if [ $? -ne 0 ]; then
+        echo "[ERROR] Failed to create virtual environment"
+        exit 1
+    fi
+    echo "[SUCCESS] Virtual environment created"
+    echo ""
+fi
+
+# 啟動虛擬環境
+echo "[INFO] Activating virtual environment..."
+source venv/bin/activate
+
+# 安裝依賴
+echo "[INFO] Installing dependencies..."
+pip install -r requirements.txt
+if [ $? -ne 0 ]; then
+    echo "[ERROR] Failed to install dependencies"
+    exit 1
+fi
+echo ""
+
+# 檢查 .env 檔案
+if [ ! -f ".env" ]; then
+    echo "[WARNING] .env file not found"
+    echo "Please create .env file with required configuration"
+    echo ""
+fi
+
+# 啟動 Flask 伺服器
+echo "[INFO] Starting Flask server..."
+echo "Server will run on http://127.0.0.1:5002"
+echo "Press Ctrl+C to stop the server"
+echo ""
+python3 app.py