Add isFollowedByCurrentUser field and hasFollowing to feed query

Updated GraphQL operations to support efficient follow status checking:
- Added isFollowedByCurrentUser field to UserSocialsFields fragment
- Removed nested followers array from UserSocialsFields (over-fetching)
- Simplified followUser/unfollowUser mutations to return minimal data
- Added hasFollowing field to GetVideoFeed query for feed mode detection
- Updated getUserFollowingFollowers query to include isFollowedByCurrentUser

These changes enable the mobile app to:
- Display correct follow/unfollow button states without client-side lookups
- Differentiate between "Following" and "Popular" feed modes
- Reduce payload size by removing unnecessary nested data

Backend handles efficient resolution via request-scoped caching.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/operations/user.gql

@@ -88,31 +88,15 @@ query GetUserTags {
 
 mutation followUser($followedUserId: Int!) {
   followUser(followedUserId: $followedUserId) {
-    username
     id
-    following {
-      id
-      username
-    }
-    followers {
-      id
-      username
-    }
+    username
   }
 }
 
 mutation unfollowUser($followedUserId: Int!) {
   unfollowUser(followedUserId: $followedUserId) {
-    username
     id
-    following {
-      id
-      username
-    }
-    followers {
-      id
-      username
-    }
+    username
   }
 }
 
@@ -123,11 +107,13 @@ query getUserFollowingFollowers {
       id
       username
       profileImageUri
+      isFollowedByCurrentUser
     }
     followers {
       id
       username
       profileImageUri
+      isFollowedByCurrentUser
     }
   }
 }