fix(security): eliminate remaining critical vulnerabilities

- SystemFixService: removed ALL shell_exec/sudo calls (30+ instances), replaced with
  safe PHP alternatives (mkdir, chmod, disk_total_space, Artisan calls)
- InstallationController: added ALLOWED_SETTINGS whitelist to prevent arbitrary
  settings manipulation via request data
- ExceptionHandler: removed dangerous npm run build execution and hardcoded
  chown/chmod paths from auto-recovery
- AuthController: fixed user enumeration timing attack by running Hash::make()
  even when user doesn't exist (constant-time comparison)
- DDoSDetectionCommand: added IP validation (FILTER_VALIDATE_IP) before blocking
  to prevent iptables manipulation with spoofed/malicious IPs
- trackRequest: now validates IP before storing in cache

app/Exceptions/Handler.php

@@ -12,7 +12,6 @@ use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;
 use Illuminate\Support\Facades\Artisan;
 use Illuminate\Support\Facades\Cache;
 use Illuminate\Support\Facades\Log;
-use Illuminate\Support\Facades\Process;
 use Illuminate\Validation\ValidationException;
 use Throwable;
 
@@ -101,10 +100,6 @@ class Handler extends ExceptionHandler
             Artisan::call('config:cache');
             Artisan::call('view:cache');
 
-            if (str_contains($exceptionClass, 'ViteManifestNotFoundException') || str_contains($message, 'Vite manifest')) {
-                $this->rebuildViteManifest();
-            }
-
             if (function_exists('opcache_reset')) {
                 @opcache_reset();
             }
@@ -122,31 +117,6 @@ class Handler extends ExceptionHandler
         }
     }
 
-    private function rebuildViteManifest(): void
-    {
-        $manifestPath = public_path('build/manifest.json');
-
-        if (! file_exists($manifestPath)) {
-            Log::warning('Vite manifest missing, attempting rebuild');
-
-            $result = Process::timeout(120)->run('npm run build');
-
-            if ($result->successful()) {
-                Log::info('Vite manifest rebuilt successfully');
-
-                if (file_exists('/var/www/atomcms/public/build')) {
-                    Process::run('chown -R www-data:www-data /var/www/atomcms/public/build');
-                    Process::run('chmod -R 775 /var/www/atomcms/public/build');
-                }
-            } else {
-                Log::error('Vite manifest rebuild failed', [
-                    'output' => $result->output(),
-                    'error' => $result->errorOutput(),
-                ]);
-            }
-        }
-    }
-
     private function handleExceptionAlert(Throwable $e): void
     {
         if (! $this->shouldAlertException($e)) {