- Add compile-time @build_timestamp to Application module
- Create ToweropsWeb.TimeHelpers module for shared time formatting
- Update footer to display 'Last deployed Xm ago · YYYY-MM-DD HH:MM:SS UTC'
- Refactor AgentLive.Helpers to delegate to shared TimeHelpers
- Consolidate duplicate time formatting logic into single module
- Timestamp updates automatically on each build/deploy
