feat: implement single binary build and env-based auth

- Unify login page styling with share page
- Add AGENTS.md with build commands and code style guidelines
- Add dev.sh and make.sh for development and production builds
- Implement single binary build with embedded frontend using embed.FS
- Change auth configuration from CLI flag to env variables (USHARE_USERNAME, USHARE_PASSWORD)
- Set default credentials: admin / ushare@123
- Fix static file serving for SPA routes

dev.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+
+set -e
+
+# 捕获 Ctrl+C 信号
+trap 'echo ""; echo "Stopping..."; kill $(jobs -p); exit 0' SIGINT SIGTERM
+
+echo "=========================================="
+echo "  Starting UShare Development Server"
+echo "=========================================="
+echo ""
+
+# 构建前端（如果需要）
+if [ ! -d "frontend/dist" ]; then
+    echo "[Frontend] Building..."
+    cd frontend && pnpm run build && cd ..
+    echo "[Frontend] Build complete!"
+fi
+
+# 创建临时嵌入目录用于编译
+mkdir -p internal/static/frontend
+if [ ! -d "internal/static/frontend/dist" ]; then
+    echo "[Setup] Creating frontend embed directory..."
+    cp -r frontend/dist internal/static/frontend/
+fi
+
+# 检查后端是否已构建
+if [ ! -f "./ushare" ]; then
+    echo "[Backend] Building..."
+    go build -o ushare .
+    echo "[Backend] Build complete!"
+fi
+
+# 创建数据目录
+mkdir -p ./data
+
+# 启动后端
+echo "[Backend] Starting..."
+./ushare -debug -address 0.0.0.0:9119 -data ./data &
+BACKEND_PID=$!
+echo "[Backend] Running on http://0.0.0.0:9119 (PID: $BACKEND_PID)"
+echo ""
+
+# 启动前端
+echo "[Frontend] Starting..."
+cd frontend && pnpm run dev &
+FRONTEND_PID=$!
+cd ..
+echo "[Frontend] Running on http://localhost:5173 (PID: $FRONTEND_PID)"
+echo ""
+
+echo "=========================================="
+echo "  All services started!"
+echo "  - Backend:  http://0.0.0.0:9119"
+echo "  - Frontend: http://0.0.0.0:5173"
+echo "=========================================="
+echo ""
+echo "Note: Frontend hot-reload is enabled. Changes to backend code require rebuilding."
+echo "Press Ctrl+C to stop all services"
+echo ""
+
+# 等待所有后台进程
+wait