Fixes three critical bugs in Telegram integration:
1. Case-insensitive username matching
- Telegram usernames are case-insensitive, but the API returns them with original casing
- Now lowercase all usernames when extracting sender identifier to match config entries
- Fixes: messages from @ArneMoor now match config entry telegram:@arnemoor
2. Entity resolution for sending replies
- resolveEntity() now strips telegram: prefix before resolving users/chats
- Fixes: "Could not resolve Telegram entity: telegram:@username" errors when sending replies
3. Improved skip logging
- Messages skipped due to allowFrom filtering now always logged (not just in verbose mode)
- Uses clear emoji indicator: ⏭️ Skipped message from...