- Added shutdown-only persistence for stats and last_heard data (SD-friendly)
- Moved retransmitted calls counting from HBlink4 to dashboard for consistency
- Added graceful permission handling and atomic file writes
- Enhanced dashboard UI with clearer RX/TX statistics semantics
- Removed periodic forwarding_stats broadcast from HBlink4
- Added installation documentation for proper file permissions
- Improved time display formatting for multi-day last_heard entries
