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

.cursor/config.json

@@ -0,0 +1,44 @@
+{
+  "rules": {
+    "preferCompositionAPI": true,
+    "strictTypes": true,
+    "noHardcodedValues": true,
+    "useDependencyInjection": true
+  },
+  "paths": {
+    "telecart_module": "module/oc_telegram_shop/upload/oc_telegram_shop",
+    "frontendAdmin": "frontend/admin",
+    "telegramShopSpa": "frontend/spa",
+    "migrations": "module/oc_telegram_shop/upload/oc_telegram_shop/database/migrations",
+    "telecartHandlers": "module/oc_telegram_shop/upload/oc_telegram_shop/src/Handlers",
+    "adminHandlers": "module/oc_telegram_shop/upload/oc_telegram_shop/bastion/Handlers",
+    "models": "module/oc_telegram_shop/upload/oc_telegram_shop/src/Models",
+    "framework": "module/oc_telegram_shop/upload/oc_telegram_shop/framework"
+  },
+  "naming": {
+    "classes": "PascalCase",
+    "methods": "camelCase",
+    "variables": "camelCase",
+    "constants": "UPPER_SNAKE_CASE",
+    "files": "PascalCase for classes, kebab-case for others",
+    "tables": "snake_case with telecart_ prefix"
+  },
+  "php": {
+    "version": "7.4+",
+    "preferVersion": "7.4+",
+    "psr12": true
+  },
+  "javascript": {
+    "version": "ES2020+",
+    "framework": "Vue 3 Composition API",
+    "stateManagement": "Pinia",
+    "uiLibrary": "PrimeVue (admin), Tailwind (spa)"
+  },
+  "database": {
+    "queryBuilder": true,
+    "migrations": true,
+    "tablePrefix": "telecart_",
+    "noForeignKeys": true
+  }
+}
+