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/local_infra.go

@@ -187,6 +187,9 @@ func pruneLocalHistory(histDir string, maxKeep int, logger *log.Logger) {
 			logger.Printf("[DEBUG] Local infra history: pruned old version %s", ts)
 		}
 	}
+	if logger != nil && toDelete > 0 {
+		logger.Printf("[INFO] [backup] Pruning old backup versions: kept %d, removed %d", maxKeep, toDelete)
+	}
 }
 
 // sanitizeTimestamp converts an RFC3339 timestamp to a filename-safe format.