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/src/services/api.ts

@@ -70,7 +70,7 @@ class ApiClient {
   async buyTickets(
     tickets: number,
     lightningAddress: string,
-    telegramUserId: number
+    displayName: string = 'Anon'
   ): Promise<BuyTicketsResponse> {
     try {
       const response = await this.client.post<ApiResponse<BuyTicketsResponse>>(
@@ -78,7 +78,7 @@ class ApiClient {
         {
           tickets,
           lightning_address: lightningAddress,
-          buyer_name: `TG:${telegramUserId}`,
+          buyer_name: displayName || 'Anon',
         }
       );
       return response.data.data;