Add Loki Logging
v1.14.0: Add Loki logging for backup/restore lifecycle Adds optional integration with loki-logger mu-plugin. Logs backup start/complete/fail, restore success/failure, scheduler skips, and updater errors. Replaces error_log() calls with structured logging. No-op when mu-plugin is absent. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>