feat: 初始化考培练系统项目

- 从服务器拉取完整代码
- 按框架规范整理项目结构
- 配置 Drone CI 测试环境部署
- 包含后端(FastAPI)、前端(Vue3)、管理端

技术栈: Vue3 + TypeScript + FastAPI + MySQL

backend/app/config/database.py

@@ -0,0 +1,49 @@
+"""数据库配置"""
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.pool import NullPool
+
+from app.core.config import get_settings
+
+settings = get_settings()
+
+# 创建异步引擎
+if settings.DEBUG:
+    # 开发环境使用 NullPool，不需要连接池参数
+    engine = create_async_engine(
+        settings.DATABASE_URL, 
+        echo=False, 
+        pool_pre_ping=True, 
+        poolclass=NullPool,
+        # 确保 MySQL 连接使用 UTF-8 字符集
+        connect_args={
+            "charset": "utf8mb4",
+            "use_unicode": True,
+            "autocommit": False,
+            "init_command": "SET character_set_client=utf8mb4, character_set_connection=utf8mb4, character_set_results=utf8mb4, collation_connection=utf8mb4_unicode_ci",
+        } if "mysql" in settings.DATABASE_URL else {},
+    )
+else:
+    # 生产环境使用连接池
+    engine = create_async_engine(
+        settings.DATABASE_URL,
+        echo=False,
+        pool_size=20,
+        max_overflow=0,
+        pool_pre_ping=True,
+        # 确保 MySQL 连接使用 UTF-8 字符集
+        connect_args={
+            "charset": "utf8mb4",
+            "use_unicode": True,
+            "autocommit": False,
+            "init_command": "SET character_set_client=utf8mb4, character_set_connection=utf8mb4, character_set_results=utf8mb4, collation_connection=utf8mb4_unicode_ci",
+        } if "mysql" in settings.DATABASE_URL else {},
+    )
+
+# 创建异步会话工厂
+SessionLocal = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+    autocommit=False,
+    autoflush=False,
+)