feat: add Telegram customers management system with admin panel

Implement comprehensive Telegram customers storage and management functionality:

Backend:
- Add database migration for telecart_customers table with indexes
- Create TelegramCustomer model with CRUD operations
- Implement TelegramCustomerService for business logic
- Add TelegramCustomerHandler for API endpoint (saveOrUpdate)
- Add TelegramCustomersHandler for admin API (getCustomers with pagination, filtering, sorting)
- Add SendMessageHandler for sending messages to customers via Telegram
- Create custom exceptions: TelegramCustomerNotFoundException, TelegramCustomerWriteNotAllowedException
- Refactor TelegramInitDataDecoder to separate decoding logic
- Add TelegramHeader enum for header constants
- Update SignatureValidator to use TelegramInitDataDecoder
- Register new routes in bastion/routes.php and src/routes.php

Frontend (Admin):
- Add CustomersView.vue component with PrimeVue DataTable
- Implement advanced filtering (text, date, boolean filters)
- Add column visibility toggle functionality
- Add global search with debounce
- Implement message sending dialog with validation
- Add Russian locale for PrimeVue components
- Add navigation link in App.vue
- Register route in router

Frontend (SPA):
- Add saveTelegramCustomer utility function
- Integrate automatic customer data saving on app initialization
- Extract user data from Telegram.WebApp.initDataUnsafe

The system automatically saves/updates customer data when users access the Telegram Mini App,
and provides admin interface for viewing, filtering, and messaging customers.

BREAKING CHANGE: None

frontend/admin/src/router/index.js

@@ -8,19 +8,21 @@ import StoreView from "@/views/StoreView.vue";
 import MainPageView from "@/views/MainPageView.vue";
 import LogsView from "@/views/LogsView.vue";
 import FormBuilderView from "@/views/FormBuilderView.vue";
+import CustomersView from "@/views/CustomersView.vue";
 
 const router = createRouter({
   history: createMemoryHistory(),
   routes: [
     {path: '/', name: 'general', component: GeneralView},
-    {path: '/orders', name: 'orders', component: OrdersView},
-    {path: '/texts', name: 'texts', component: TextsView},
-    {path: '/telegram', name: 'telegram', component: TelegramView},
-    {path: '/metrics', name: 'metrics', component: MetricsView},
-    {path: '/store', name: 'store', component: StoreView},
-    {path: '/mainpage', name: 'mainpage', component: MainPageView},
-    {path: '/logs', name: 'logs', component: LogsView},
+    {path: '/customers', name: 'customers', component: CustomersView},
     {path: '/formbuilder', name: 'formbuilder', component: FormBuilderView},
+    {path: '/logs', name: 'logs', component: LogsView},
+    {path: '/mainpage', name: 'mainpage', component: MainPageView},
+    {path: '/metrics', name: 'metrics', component: MetricsView},
+    {path: '/orders', name: 'orders', component: OrdersView},
+    {path: '/store', name: 'store', component: StoreView},
+    {path: '/telegram', name: 'telegram', component: TelegramView},
+    {path: '/texts', name: 'texts', component: TextsView},
   ],
 });