Add SQLite database for Telegram bot user/group settings

- Replace Redis/in-memory storage with SQLite for persistence
- Add database.ts service with tables for users, groups, purchases, participants
- Update state.ts and groupState.ts to use SQLite backend
- Fix buyer_name to use display name instead of Telegram ID
- Remove legacy reminder array handlers (now using 3-slot system)
- Add better-sqlite3 dependency, remove ioredis
- Update env.example with BOT_DATABASE_PATH option
- Add data/ directory to .gitignore for database files

telegram_bot/package.json

@@ -19,13 +19,14 @@
   "license": "MIT",
   "dependencies": {
     "axios": "^1.6.2",
+    "better-sqlite3": "^9.4.3",
     "dotenv": "^16.3.1",
-    "ioredis": "^5.3.2",
     "node-telegram-bot-api": "^0.64.0",
     "qrcode": "^1.5.3",
     "winston": "^3.11.0"
   },
   "devDependencies": {
+    "@types/better-sqlite3": "^7.6.8",
     "@types/node": "^20.10.4",
     "@types/node-telegram-bot-api": "^0.64.2",
     "@types/qrcode": "^1.5.5",