feat: add WonderQ admin backend

Add FastAPI admin/public API service, database setup, Docker deployment files, docs, and tests.

app/main.py

@@ -0,0 +1,43 @@
+import logging
+from fastapi import FastAPI, HTTPException, Request
+from fastapi.exceptions import RequestValidationError
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+from .config import get_settings
+from .routers import admin, public
+
+
+def create_app() -> FastAPI:
+    settings = get_settings()
+    logging.basicConfig(level=settings.log_level.upper())
+
+    app = FastAPI(title="WonderQ Admin API")
+    origins = ["*"] if settings.cors_origins == "*" else [item.strip() for item in settings.cors_origins.split(",") if item.strip()]
+    app.add_middleware(
+        CORSMiddleware,
+        allow_origins=origins,
+        allow_credentials=True,
+        allow_methods=["*"],
+        allow_headers=["*"],
+    )
+
+    @app.exception_handler(RequestValidationError)
+    async def validation_exception_handler(_request: Request, exc: RequestValidationError):
+        first = exc.errors()[0] if exc.errors() else {}
+        return JSONResponse(status_code=400, content={"message": first.get("msg", "请求参数不正确")})
+
+    @app.exception_handler(HTTPException)
+    async def http_exception_handler(_request: Request, exc: HTTPException):
+        return JSONResponse(status_code=exc.status_code, content={"message": exc.detail})
+
+    @app.exception_handler(Exception)
+    async def unhandled_exception_handler(request: Request, exc: Exception):
+        request.app.logger.exception(exc) if hasattr(request.app, "logger") else logging.exception(exc)
+        return JSONResponse(status_code=500, content={"message": "服务暂时不可用"})
+
+    app.include_router(public.router)
+    app.include_router(admin.router)
+    return app
+
+
+app = create_app()