Set FastAPI title to `Open WebUI`

This affects the generated OpenAPI (`/docs` and `/openapi.json`).

backend/open_webui/main.py

@@ -426,6 +426,7 @@ async def lifespan(app: FastAPI):
 
 
 app = FastAPI(
+    title="Open WebUI",
     docs_url="/docs" if ENV == "dev" else None,
     openapi_url="/openapi.json" if ENV == "dev" else None,
     redoc_url=None,