refactor(database): 重构数据库存储实现，使用SQLAlchemy ORM替代原始SQL操作

- 删除旧的async_db.py和async_sqlite_db.py实现
- 新增SQLAlchemy ORM模型和数据库会话管理
- 统一各平台存储实现到_store_impl.py文件
- 添加数据库初始化功能支持
- 更新.gitignore和pyproject.toml依赖配置
- 优化文件存储路径和命名规范

pyproject.toml

@@ -9,6 +9,8 @@ dependencies = [
     "aiofiles~=23.2.1",
     "aiomysql==0.2.0",
     "aiosqlite>=0.21.0",
+    "alembic>=1.16.5",
+    "asyncmy>=0.2.10",
     "fastapi==0.110.2",
     "httpx==0.28.1",
     "jieba==0.42.1",
@@ -24,6 +26,7 @@ dependencies = [
     "python-dotenv==1.0.1",
     "redis~=4.6.0",
     "requests==2.32.3",
+    "sqlalchemy>=2.0.43",
     "tenacity==8.2.2",
     "uvicorn==0.29.0",
     "wordcloud==1.9.3",