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/Models/User.php

@@ -43,6 +43,7 @@ class User extends Authenticatable implements MustVerifyEmail
         'two_factor_secret',
         'two_factor_enabled',
         'banner',
+        'notification_preferences',
     ];
 
     protected $hidden = [
@@ -51,11 +52,46 @@ class User extends Authenticatable implements MustVerifyEmail
     ];
 
     protected $casts = [
-        'email_verified_at'  => 'datetime',
-        'password'           => 'hashed',
-        'two_factor_enabled' => 'boolean',
+        'email_verified_at'          => 'datetime',
+        'password'                   => 'hashed',
+        'two_factor_enabled'         => 'boolean',
+        'notification_preferences'   => 'array',
     ];
 
+    // Defaults for each preference key (true = on, false = off)
+    private const NOTIF_DEFAULTS = [
+        'notif_new_comment'        => true,
+        'notif_new_reply'          => true,
+        'notif_comment_like'       => true,
+        'notif_video_like'         => true,
+        'notif_new_subscriber'     => true,
+        'notif_new_video_from_sub' => true,
+        'notif_new_post_from_sub'  => true,
+        'notif_new_user_reg'       => true,
+        'email_new_comment'        => true,
+        'email_new_reply'          => true,
+        'email_comment_like'       => false,
+        'email_video_like'         => false,
+        'email_new_subscriber'     => true,
+        'email_new_video_from_sub' => true,
+        'email_new_post_from_sub'  => false,
+        'email_video_processed'    => true,
+        'email_new_user_reg'       => true,
+        'email_weekly_digest'      => true,
+    ];
+
+    public function notificationPref(string $key): bool
+    {
+        $prefs   = $this->notification_preferences ?? [];
+        $default = self::NOTIF_DEFAULTS[$key] ?? true;
+        return isset($prefs[$key]) ? (bool) $prefs[$key] : $default;
+    }
+
+    public static function notifDefaults(): array
+    {
+        return self::NOTIF_DEFAULTS;
+    }
+
     protected $appends = ['avatar_url', 'banner_url'];
 
     // Auto-generate a unique slug-based username when creating a user without one