fix(backend): serve frontend at root path and move meta info to /api/meta

backend/app/main_spa.py

@@ -47,8 +47,8 @@ app.include_router(upload.router, prefix=f"{settings.API_V1_STR}/upload", tags=[
 app.include_router(results.router, prefix=f"{settings.API_V1_STR}/results", tags=["results"])
 
 
-@app.get("/")
-async def root():
+@app.get("/api/meta")
+async def root_meta():
     return {
         "name": settings.APP_NAME,
         "version": settings.APP_VERSION,
@@ -70,7 +70,17 @@ if frontend_dist_path.exists():
     @app.get("/{full_path:path}", include_in_schema=False)
     async def serve_spa(full_path: str):
         """Serve frontend SPA - all routes go to index.html"""
+        # 如果是 API 路径，且没有被前面路由捕获，返回 404
+        if full_path.startswith("api/"):
+            return {"detail": "Not Found"}, 404
+
+        # 处理根路径 ""
+        if full_path == "" or full_path == "/":
+            return FileResponse(frontend_dist_path / "index.html")
+
         file_path = frontend_dist_path / full_path
         if file_path.exists() and file_path.is_file():
             return FileResponse(file_path)
+
+        # SPA 路由：返回 index.html
         return FileResponse(frontend_dist_path / "index.html")