feat: comprehensive INFO/WARN/ERROR logging across all controller modules

Add structured operational logging at INFO, WARN, and ERROR levels to
every controller module. Standardize custom prefixes ([GEO], [SCHED],
[SYNC]) to use [INFO/WARN/ERROR] [module] format. Fix misleveled logs
(WARN->ERROR for data loss scenarios, WARN->INFO for routine operations).

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

controller/internal/backup/restic.go

@@ -207,6 +207,7 @@ func (r *ResticManager) Snapshot(repoPath string, paths []string, tags []string)
 			result.Duration, result.SnapshotID, result.FilesNew, result.FilesChanged, result.DataAdded)
 	}
 
+	r.logger.Printf("[INFO] [backup] Restic snapshot complete for %s", repoPath)
 	return result, nil
 }
 
@@ -264,6 +265,7 @@ func (r *ResticManager) Check(repoPath string) error {
 	if r.debug {
 		r.logger.Printf("[DEBUG] [restic] Check: repo=%s OK, completed in %s", repoPath, time.Since(start))
 	}
+	r.logger.Printf("[INFO] [backup] Restic check passed for repo %s", repoPath)
 	return nil
 }