Bust avatar/banner cache so new image shows on all pages

After my previous fix the upload succeeds, but the avatar path is always
.../profile/avatar.<ext>, so its media URL never changes. Pages other than the
channel (which cache-busts with ?t=) kept serving the browser-cached OLD image
— the user "still saw the old avatar" on /videos.

- avatar_url / banner_url accessors append ?v=<updated_at timestamp>.
- updateAvatar / updateBanner now bump updated_at explicitly (the path is
  unchanged, so Eloquent wouldn't otherwise touch it), changing ?v so every
  page fetches the new image.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

app/Http/Controllers/UserController.php

@@ -565,7 +565,11 @@ class UserController extends Controller
             rename($tempPath, $destPath);
         }
 
-        $user->update(['avatar' => $relPath]);
+        // Bump updated_at even when $relPath is unchanged (avatar.png -> avatar.png)
+        // so avatar_url's ?v cache-buster changes and every page shows the new image.
+        $user->avatar = $relPath;
+        $user->updated_at = now();
+        $user->save();
 
         if ($nas->isEnabled() && file_exists($destPath)) {
             $nas->syncAvatar($user, $destPath);
@@ -602,7 +606,11 @@ class UserController extends Controller
             rename($tempPath, $destPath);
         }
 
-        $user->update(['banner' => $relPath]);
+        // Bump updated_at even when $relPath is unchanged so banner_url's ?v buster
+        // changes and the new banner shows everywhere (see updateAvatar).
+        $user->banner = $relPath;
+        $user->updated_at = now();
+        $user->save();
 
         if ($nas->isEnabled() && file_exists($destPath)) {
             $nas->syncCover($user, $destPath);