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/Notifications/WeeklyDigestNotification.php

@@ -0,0 +1,60 @@
+<?php
+
+namespace App\Notifications;
+
+use App\Models\User;
+use Illuminate\Notifications\Messages\MailMessage;
+use Illuminate\Notifications\Notification;
+use Illuminate\Support\Facades\DB;
+
+class WeeklyDigestNotification extends Notification
+{
+    public array $stats;
+
+    public function __construct(public User $creator)
+    {
+        $videoIds = $creator->videos()->pluck('id');
+
+        $views = DB::table('video_views')
+            ->whereIn('video_id', $videoIds)
+            ->where('created_at', '>=', now()->subWeek())
+            ->count();
+
+        $likes = DB::table('video_likes')
+            ->whereIn('video_id', $videoIds)
+            ->where('created_at', '>=', now()->subWeek())
+            ->count();
+
+        $newSubs = DB::table('user_subscriptions')
+            ->where('channel_id', $creator->id)
+            ->where('created_at', '>=', now()->subWeek())
+            ->count();
+
+        $topVideo = $creator->videos()
+            ->withCount(['viewers as week_views' => fn($q) => $q->where('video_views.created_at', '>=', now()->subWeek())])
+            ->orderByDesc('week_views')
+            ->first();
+
+        $this->stats = [
+            'views'     => $views,
+            'likes'     => $likes,
+            'new_subs'  => $newSubs,
+            'top_video' => $topVideo,
+        ];
+    }
+
+    public function via(object $notifiable): array
+    {
+        return $notifiable->notificationPref('email_weekly_digest') ? ['mail'] : [];
+    }
+
+    public function toMail(object $notifiable): MailMessage
+    {
+        return (new MailMessage)
+            ->subject('Your weekly TAKEONE summary 📊')
+            ->view('emails.weekly-digest', [
+                'creator'   => $this->creator,
+                'stats'     => $this->stats,
+            ]);
+    }
+}