feat(core): 初始化 Key-IP Sentinel 服务与部署骨架

- 搭建 FastAPI、Redis、PostgreSQL、Nginx 与 Docker Compose 基础结构
- 实现反向代理、首用绑定、拦截告警、归档任务和管理接口
- 提供 Vue3 管理后台初版，以及 uv/requirements 双依赖配置

app/models/db.py

@@ -0,0 +1,48 @@
+from __future__ import annotations
+
+from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import Settings
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+_engine: AsyncEngine | None = None
+_session_factory: async_sessionmaker[AsyncSession] | None = None
+
+
+def init_db(settings: Settings) -> None:
+    global _engine, _session_factory
+    if _engine is not None and _session_factory is not None:
+        return
+
+    _engine = create_async_engine(
+        settings.pg_dsn,
+        pool_pre_ping=True,
+        pool_size=20,
+        max_overflow=40,
+    )
+    _session_factory = async_sessionmaker(_engine, expire_on_commit=False)
+
+
+def get_engine() -> AsyncEngine:
+    if _engine is None:
+        raise RuntimeError("Database engine has not been initialized.")
+    return _engine
+
+
+def get_session_factory() -> async_sessionmaker[AsyncSession]:
+    if _session_factory is None:
+        raise RuntimeError("Database session factory has not been initialized.")
+    return _session_factory
+
+
+async def close_db() -> None:
+    global _engine, _session_factory
+    if _engine is not None:
+        await _engine.dispose()
+    _engine = None
+    _session_factory = None