Fix reminder scheduling and add group features

- Fix reminder duplicate bug: use slot-only keys to prevent multiple reminders when settings change
- Add New Jackpot announcement delay setting for groups (default 5 min)
- Cancel unpaid purchases after draw completes (prevents payments for past rounds)
- Add BotFather commands template file
- Update README documentation

telegram_bot/src/services/groupState.ts

@@ -81,6 +81,16 @@ class GroupStateManager {
     return botDatabase.updateAnnouncementDelay(groupId, seconds);
   }
 
+  /**
+   * Update new jackpot announcement delay
+   */
+  async updateNewJackpotDelay(
+    groupId: number,
+    minutes: number
+  ): Promise<GroupSettings | null> {
+    return botDatabase.updateNewJackpotDelay(groupId, minutes);
+  }
+
   /**
    * Get groups with specific feature enabled
    */