feat(mail): make notification failures non-fatal

Add App\Support\SafeNotifier that wraps $notifiable->notify() in a
Throwable guard with a logged warning, so SMTP outages (the current
Gmail 535 errors) no longer propagate as a 500 to the user. Apply to
the two hot paths that were still unprotected: CommentController
(new comment, reply, like) and RegisteredUserController (super-admin
registration alert). User::sendEmailVerificationNotification() is
wrapped inline for the same reason.

Also add docs/mail-setup.md covering the three delivery options:
Gmail app password (quick), Mailgun, Postmark — with the exact .env
keys for each.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

app/Http/Controllers/CommentController.php

@@ -9,6 +9,7 @@ use App\Notifications\NewCommentLikeNotification;
 use App\Notifications\NewCommentNotification;
 use App\Notifications\NewReplyNotification;
 use App\Services\LlmLyricsService;
+use App\Support\SafeNotifier;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Auth;
 
@@ -71,12 +72,12 @@ class CommentController extends Controller
             // Reply — notify the parent comment's author
             $parent = Comment::find($request->parent_id);
             if ($parent && $parent->user_id !== $commenter->id) {
-                $parent->user->notify(new NewReplyNotification($video, $comment, $commenter));
+                SafeNotifier::send($parent->user, new NewReplyNotification($video, $comment, $commenter));
             }
         } else {
             // Top-level comment — notify the video owner
             if ($video->user_id !== $commenter->id) {
-                $video->user->notify(new NewCommentNotification($video, $comment, $commenter));
+                SafeNotifier::send($video->user, new NewCommentNotification($video, $comment, $commenter));
             }
         }
 
@@ -162,7 +163,8 @@ class CommentController extends Controller
             if ($comment->user_id !== $userId) {
                 $video = $comment->video;
                 if ($video) {
-                    $comment->user->notify(
+                    SafeNotifier::send(
+                        $comment->user,
                         new NewCommentLikeNotification($video, $comment, Auth::user())
                     );
                 }