fix: ensure sanctum guard driver is always registered

Two changes:

1. app/Http/Middleware/TeacherPortalAuthenticate.php:
   - Added try-catch around Auth::guard('sanctum')->user() to match
     the defensive pattern used by MultiAuth and
     EnsurePrintRequestsAdminAccess middleware.

2. app/Providers/AppServiceProvider.php:
   - Added Auth::resolved() callback to re-register the sanctum guard
     driver as a safety net. This ensures the driver is available even
     when a stale cached config lacks the auth.guards.sanctum entry,
     or when SanctumServiceProvider::configureGuard() runs before
     the AuthManager is ready to accept custom guard creators.

app/Providers/AppServiceProvider.php

@@ -37,6 +37,7 @@ use App\Services\Invoices\InvoiceTuitionService;
 use App\Services\Staff\StaffTimeOffLinkService;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Routing\Redirector;
+use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Facades\Gate;
 use Illuminate\Support\ServiceProvider;
 
@@ -88,6 +89,26 @@ class AppServiceProvider extends ServiceProvider
         Gate::policy(Setting::class, SettingPolicy::class);
         Gate::policy(ClassProgressReport::class, ClassProgressReportPolicy::class);
 
+        // Re-register the sanctum guard driver to ensure it is available even
+        // when a stale cached config lacks the sanctum auth guard entry.
+        Auth::resolved(function ($auth): void {
+            $auth->extend('sanctum', function ($app, $name, array $config) use ($auth) {
+                return tap(
+                    new \Illuminate\Auth\RequestGuard(
+                        new \Laravel\Sanctum\Guard(
+                            $auth,
+                            config('sanctum.expiration'),
+                            $config['provider'] ?? null,
+                            config('sanctum.last_used_at', true),
+                        ),
+                        request(),
+                        $auth->createUserProvider($config['provider'] ?? null),
+                    ),
+                    fn ($guard) => app()->refresh('request', $guard, 'setRequest'),
+                );
+            });
+        });
+
         $this->app->resolving(FormRequest::class, function (FormRequest $request, $app): void {
             $request->setContainer($app)->setRedirector($app->make(Redirector::class));
         });