Add full notification preferences system

Users can now control which in-app and email notifications they receive
from their Settings tab on their channel page.

Bell (in-app) preferences:
- New comment on my video (default: on)
- Reply to my comment (default: on)
- Comment liked (default: on)
- Video liked (default: on)
- New subscriber (default: on)
- New video from channels I follow (default: on)
- New post from channels I follow (default: on)
- New user registration — super admins only (default: on)

Email preferences (same set plus):
- Comment liked (default: off — too noisy)
- Video liked (default: off — too noisy)
- New post from channels I follow (default: off)
- My video finished processing (default: on)
- Weekly activity digest every Monday (default: on)
- New user registration — super admins only (default: on)

Implementation:
- Migration: notification_preferences JSON column on users table
- User::notificationPref($key) helper with typed defaults
- All existing notification classes updated to check prefs in via()
- 4 new notification classes: NewSubscriberNotification,
  VideoLikedNotification, NewPostNotification, WeeklyDigestNotification
- 8 new email views matching existing dark theme
- SendWeeklyDigest artisan command, scheduled every Monday 09:00
- NewSubscriberNotification wired into UserController::toggleSubscribe
- VideoLikedNotification wired into UserController::toggleLike
- NewPostNotification wired into PostController::store (to all subscribers)
- Bell renderer updated for new_subscriber, video_like, new_post types
- Preferences saved via AJAX (POST /settings/notifications) — instant
  toggle with automatic revert on failure

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

app/Http/Controllers/PostController.php

@@ -6,6 +6,7 @@ use App\Models\Post;
 use App\Models\PostImage;
 use App\Models\PostVideo;
 use App\Models\User;
+use App\Notifications\NewPostNotification;
 use App\Services\NasSyncService;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Auth;
@@ -115,6 +116,12 @@ class PostController extends Controller
             }
         }
 
+        // Notify subscribers of new post
+        $author = $user->fresh();
+        $author->subscribers()->each(function (User $subscriber) use ($post, $author) {
+            try { $subscriber->notify(new NewPostNotification($post, $author)); } catch (\Throwable) {}
+        });
+
         return back()->with('toast_success', 'Post shared!');
     }