Wire dashboard into app

- Add web_user, web_password, secret_key as optional params to create_app
- Conditionally mount dashboard router when all three are set
- Pass settings from main.py to create_app
- Add tests for no dashboard/login routes when config absent

Made-with: Cursor

src/ntr_fetcher/main.py

@@ -80,6 +80,9 @@ def run() -> None:
         admin_token=settings.admin_token,
         show_day=settings.show_day,
         show_hour=settings.show_hour,
+        web_user=settings.web_user,
+        web_password=settings.web_password,
+        secret_key=settings.secret_key,
     )
 
     @app.on_event("startup")