feat: 创建 FastAPI 项目骨架（config + main + 依赖管理）

app/main.py

@@ -0,0 +1,27 @@
+import logging
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+from app.config import settings
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    logging.basicConfig(
+        level=getattr(logging, settings.log_level),
+        format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
+    )
+    yield
+
+
+app = FastAPI(
+    title="广西政府采购网公告监控系统",
+    version="2.0.0",
+    lifespan=lifespan,
+    docs_url="/docs" if settings.debug else None,
+    redoc_url=None,
+)
+
+
+@app.get("/health")
+async def health():
+    return {"status": "ok"}