feat: unify sync functionality with event-driven UI updates

- Refactored navbar sync button to dispatch 'sync-completed' event
- Configs page: removed duplicate 'Импорт с сервера' button, added auto-refresh on sync
- Projects page: wrapped initialization in DOMContentLoaded, added auto-refresh on sync
- Pricelists page: added auto-refresh on sync completion
- Consistent UX: all lists update automatically after 'Синхронизация' button click
- Removed code duplication: importConfigsFromServer() function no longer needed
- Event-driven architecture enables easy extension to other pages

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

web/templates/base.html

@@ -285,6 +285,14 @@
                     showToast(successMessage, 'success');
                     // Update last sync time - removed since dropdown is gone
                     // loadLastSyncTime();
+
+                    // Dispatch custom event for pages to react to sync completion
+                    window.dispatchEvent(new CustomEvent('sync-completed', {
+                        detail: {
+                            endpoint: endpoint,
+                            data: data
+                        }
+                    }));
                 } else if (resp.status === 423) {
                     const reason = data.reason_text || data.error || 'Синхронизация заблокирована.';
                     showToast(reason, 'error');