Notify super admins on new user registration (bell + email)

When a new user registers, all super_admin users receive:
- A database notification shown in the bell (type: new_user), with the
  new user's avatar and a link to their channel
- An email congratulating them with the new member's name, email,
  join date, gender, and nationality, plus a View Profile CTA

Notification rendering in app.blade.php refactored into notifHref() and
notifThumb() helpers so new_user notifications link to /channel/{slug}
and show a circular avatar instead of a video thumbnail. Also fixed the
legacy /storage/thumbnails/ path to /media/thumbnails/ for video notifications.

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

app/Http/Controllers/Auth/RegisteredUserController.php

@@ -4,6 +4,7 @@ namespace App\Http\Controllers\Auth;
 
 use App\Http\Controllers\Controller;
 use App\Models\User;
+use App\Notifications\NewUserRegistered;
 use App\Rules\NotDisposableEmail;
 use Illuminate\Auth\Events\Registered;
 use Illuminate\Http\Request;
@@ -45,6 +46,11 @@ class RegisteredUserController extends Controller
 
         event(new Registered($user));
 
+        // Notify all super admins of the new registration
+        User::where('role', 'super_admin')->each(function (User $admin) use ($user) {
+            $admin->notify(new NewUserRegistered($user));
+        });
+
         auth()->login($user);
 
         return redirect()->route('verification.notice');