[Multi-User Part 2]: Add login pages and gate access to application behind login wall (#503)

- Make most routes conditional on authentication *if anonymous mode is not enabled*. If anonymous mode is enabled, it scaffolds a default user and uses that for all application interactions.
- Add a basic login page and add routes for redirecting the user if logged in

src/database/adapters/__init__.py

@@ -73,8 +73,7 @@ async def create_google_user(token: dict) -> KhojUser:
 
 
 async def get_user_by_token(token: dict) -> KhojUser:
-    user_info = token.get("userinfo")
-    google_user = await GoogleUser.objects.filter(sub=user_info.get("sub")).select_related("user").afirst()
+    google_user = await GoogleUser.objects.filter(sub=token.get("sub")).select_related("user").afirst()
     if not google_user:
         return None
     return google_user.user