Add Pushover notification channel and improve status detection

Introduces Pushover as a new notification channel with priority-based alerts, device targeting, and custom sounds. Enhances domain status detection for .nl and .eu domains, ensuring accurate handling when expiration dates or explicit status flags are missing. Fixes PHP 8.x compatibility issues with null parameters in date functions and improves error handling and logging by replacing error_log() with a centralized Logger service. Updates documentation and migrations for version 1.1.1.

app/Controllers/UserController.php

@@ -179,7 +179,11 @@ class UserController extends Controller
                 $notificationService->notifyWelcome($userId, $username);
             } catch (\Exception $e) {
                 // Don't fail user creation if notification fails
-                error_log("Failed to create welcome notification: " . $e->getMessage());
+                $logger = new \App\Services\Logger();
+                $logger->error("Failed to create welcome notification", [
+                    'user_id' => $userId,
+                    'error' => $e->getMessage()
+                ]);
             }
 
             $_SESSION['success'] = 'User created successfully';