refactor: add KV cache, env validation, logger types, constants

- Add KV cache abstraction layer (src/services/kv-cache.ts)
- Add Zod-based env validation (src/utils/env-validation.ts)
- Improve logger types: any → unknown for type safety
- Add centralized constants file (src/constants/index.ts)
- Fix security.ts unused import

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

src/constants/index.ts

@@ -0,0 +1,180 @@
+/**
+ * Constants for telegram-bot-workers
+ *
+ * Centralized magic strings and configuration values for better maintainability.
+ *
+ * Usage:
+ *   import { SESSION_KEYS, MESSAGE_MARKERS, sessionKey } from './constants';
+ *   const key = sessionKey(SESSION_KEYS.DELETE_CONFIRM, userId);
+ */
+
+/**
+ * Session key prefixes for KV storage
+ */
+export const SESSION_KEYS = {
+  DELETE_CONFIRM: 'delete_confirm',
+  SERVER_ORDER_CONFIRM: 'server_order_confirm',
+  SERVER_SESSION: 'server_session',
+  RATE_LIMIT: 'rate_limit',
+  NOTIFICATION: 'notification',
+} as const;
+
+/**
+ * Message markers for AI response processing
+ *
+ * These markers control how responses are processed:
+ * - DIRECT: Pass through response without AI reinterpretation
+ * - KEYBOARD: Indicates inline keyboard JSON data follows
+ * - KEYBOARD_END: Marks end of keyboard data
+ * - PASSTHROUGH: Return to normal conversation flow
+ */
+export const MESSAGE_MARKERS = {
+  DIRECT: '__DIRECT__',
+  KEYBOARD: '__KEYBOARD__',
+  KEYBOARD_END: '__END__',
+  PASSTHROUGH: '__PASSTHROUGH__',
+} as const;
+
+/**
+ * Keyboard types for inline buttons
+ */
+export const KEYBOARD_TYPES = {
+  DOMAIN_REGISTER: 'domain_register',
+  SERVER_ORDER: 'server_order',
+} as const;
+
+/**
+ * Callback data prefixes for inline keyboard buttons
+ *
+ * Format: prefix:action:params
+ * Examples:
+ *   - domain_reg:confirm:example.com:15000
+ *   - server_order:confirm:order_123
+ */
+export const CALLBACK_PREFIXES = {
+  DOMAIN_REGISTER_CONFIRM: 'confirm_domain_register',
+  DOMAIN_REGISTER_CANCEL: 'cancel_domain_register',
+  SERVER_ORDER_CONFIRM: 'confirm_server_order',
+  SERVER_ORDER_CANCEL: 'cancel_server_order',
+  DELETE_CONFIRM: 'confirm_delete',
+  DELETE_CANCEL: 'cancel_delete',
+} as const;
+
+/**
+ * Transaction statuses for deposit system
+ */
+export const TRANSACTION_STATUS = {
+  PENDING: 'pending',
+  CONFIRMED: 'confirmed',
+  CANCELLED: 'cancelled',
+  REJECTED: 'rejected',
+} as const;
+
+/**
+ * Transaction types for deposit system
+ */
+export const TRANSACTION_TYPE = {
+  DEPOSIT: 'deposit',
+  WITHDRAWAL: 'withdrawal',
+  REFUND: 'refund',
+} as const;
+
+/**
+ * Server order statuses
+ */
+export const SERVER_ORDER_STATUS = {
+  PENDING: 'pending',
+  PROVISIONING: 'provisioning',
+  ACTIVE: 'active',
+  SUSPENDED: 'suspended',
+  TERMINATED: 'terminated',
+  FAILED: 'failed',
+} as const;
+
+/**
+ * Server actions
+ */
+export const SERVER_ACTION = {
+  RECOMMEND: 'recommend',
+  ORDER: 'order',
+  START: 'start',
+  STOP: 'stop',
+  DELETE: 'delete',
+  LIST: 'list',
+  INFO: 'info',
+  IMAGES: 'images',
+} as const;
+
+/**
+ * Domain actions
+ */
+export const DOMAIN_ACTION = {
+  REGISTER: 'register',
+  CHECK: 'check',
+  WHOIS: 'whois',
+  LIST: 'list',
+  INFO: 'info',
+  GET_NS: 'get_ns',
+  SET_NS: 'set_ns',
+  PRICE: 'price',
+  CHEAPEST: 'cheapest',
+} as const;
+
+/**
+ * Deposit actions
+ */
+export const DEPOSIT_ACTION = {
+  BALANCE: 'balance',
+  ACCOUNT: 'account',
+  REQUEST: 'request',
+  HISTORY: 'history',
+  CANCEL: 'cancel',
+  PENDING: 'pending',
+  CONFIRM: 'confirm',
+  REJECT: 'reject',
+} as const;
+
+/**
+ * Helper to create session key with user ID
+ *
+ * @param prefix - Session key prefix (from SESSION_KEYS)
+ * @param userId - User ID (telegram_id or user identifier)
+ * @returns Formatted session key
+ *
+ * @example
+ * const key = sessionKey(SESSION_KEYS.DELETE_CONFIRM, '123456');
+ * // Returns: 'delete_confirm:123456'
+ */
+export function sessionKey(prefix: string, userId: string | number): string {
+  return `${prefix}:${userId}`;
+}
+
+/**
+ * Helper to parse session key
+ *
+ * @param key - Full session key
+ * @returns Object with prefix and userId, or null if invalid
+ *
+ * @example
+ * const parsed = parseSessionKey('delete_confirm:123456');
+ * // Returns: { prefix: 'delete_confirm', userId: '123456' }
+ */
+export function parseSessionKey(key: string): { prefix: string; userId: string } | null {
+  const parts = key.split(':');
+  if (parts.length !== 2) return null;
+  return { prefix: parts[0], userId: parts[1] };
+}
+
+/**
+ * Type guards for type safety
+ */
+export type SessionKeyPrefix = typeof SESSION_KEYS[keyof typeof SESSION_KEYS];
+export type MessageMarker = typeof MESSAGE_MARKERS[keyof typeof MESSAGE_MARKERS];
+export type KeyboardType = typeof KEYBOARD_TYPES[keyof typeof KEYBOARD_TYPES];
+export type CallbackPrefix = typeof CALLBACK_PREFIXES[keyof typeof CALLBACK_PREFIXES];
+export type TransactionStatus = typeof TRANSACTION_STATUS[keyof typeof TRANSACTION_STATUS];
+export type TransactionType = typeof TRANSACTION_TYPE[keyof typeof TRANSACTION_TYPE];
+export type ServerOrderStatus = typeof SERVER_ORDER_STATUS[keyof typeof SERVER_ORDER_STATUS];
+export type ServerAction = typeof SERVER_ACTION[keyof typeof SERVER_ACTION];
+export type DomainAction = typeof DOMAIN_ACTION[keyof typeof DOMAIN_ACTION];
+export type DepositAction = typeof DEPOSIT_ACTION[keyof typeof DEPOSIT_ACTION];