Convert all logs to structured logging for consistency

[kaisoz]

PR #328 converts the six [Mesh Event] log lines to structured Warnw/Infow so machine consumers can parse them. The remaining ~400 printf-style call sites (logger.Debugf/Infof/Warnf/Errorf) are still prose.

Convert them to the w-variants with key-value fields for consistency, so any line can be consumed programmatically without regexing message text.

Notes:

• Mechanical but large; best done in per-package chunks to keep review manageable.
• Reuse the field vocabulary started in Structured [Mesh Event] logs #328(event, peer, timestamp, key) where applicable.