fix: enhance notifications and validation features

- Added URL validation for notification providers to ensure only valid http/https URLs are accepted.
- Implemented tests for URL validation scenarios in the Notifications component.
- Updated translations for error messages related to invalid URLs in multiple languages.
- Introduced new hooks for managing security headers and access lists in tests.
- Enhanced the ProviderForm component to reset state correctly when switching between add and edit modes.
- Improved user feedback with update indicators after saving changes to notification providers.
- Added mock implementations for new hooks in various test files to ensure consistent testing behavior.

frontend/src/pages/__tests__/ProxyHosts-bulk-acl.test.tsx

@@ -58,6 +58,10 @@ vi.mock('../../api/settings', () => ({
   getSettings: vi.fn(),
 }));
 
+vi.mock('../../hooks/useSecurityHeaders', () => ({
+  useSecurityHeaderProfiles: vi.fn(() => ({ data: [], isLoading: false, error: null })),
+}));
+
 const mockProxyHosts = [
   createMockProxyHost({ uuid: 'host-1', name: 'Test Host 1', domain_names: 'test1.example.com', forward_host: '192.168.1.10' }),
   createMockProxyHost({ uuid: 'host-2', name: 'Test Host 2', domain_names: 'test2.example.com', forward_host: '192.168.1.20' }),