feat: unified logging module and remove redundant first_run logic

- Add logger.py with TimedRotatingFileHandler (daily rotation, 30-day retention)
- Replace all print() in migrate.py with logging calls
- Add logging to sync.py for sync status tracking
- Refactor watch.py to use logger.py, remove duplicate first_run branch
- All logs now go to logs/app.log consistently
- Add logging config section to config.yaml, add logs/ to .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -21,6 +21,7 @@ Desktop.ini
 .DS_Store
 
 # Logs
+logs/
 *.log
 watch.log