feat: new file

backend/app/main.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+from fastapi import FastAPI, Request
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+from sqlalchemy.exc import OperationalError
+
+from .settings import settings
+from .routes import ai, debug, metrics, trend
+from .services.db_sample import print_db_sample_to_logs
+
+
+app = FastAPI(title="Crawl BI Backend", version="0.1.0")
+
+@app.exception_handler(OperationalError)
+async def db_operational_error_handler(_: Request, exc: OperationalError):
+    return JSONResponse(
+        status_code=503,
+        content={
+            "detail": "数据库连接失败（请检查 MYSQL_HOST/USER/PASSWORD 以及 MySQL 授权 host/IP 白名单）。",
+            "error": str(exc.orig) if getattr(exc, "orig", None) else str(exc),
+        },
+    )
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=settings.cors_origins_list,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+app.include_router(metrics.router, prefix="/api/metrics", tags=["metrics"])
+app.include_router(trend.router, prefix="/api/trend", tags=["trend"])
+app.include_router(ai.router, prefix="/api/ai", tags=["ai"])
+app.include_router(debug.router, prefix="/api/debug", tags=["debug"])
+
+
+@app.on_event("startup")
+def _startup_print_sample() -> None:
+    if settings.debug_print_db_sample:
+        print_db_sample_to_logs()
+