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/settings/settings.go

@@ -183,7 +183,7 @@ func Load(path string, logger *log.Logger) (*Settings, error) {
 		return nil, fmt.Errorf("parsing settings file: %w", err)
 	}
 
-	logger.Printf("[DEBUG] Settings loaded from %s", path)
+	logger.Printf("[INFO] [settings] Loaded settings from %s", path)
 	if s.debug {
 		s.log.Printf("[DEBUG] [settings] loaded: storage_paths=%d integrations=%d pending_events=%d",
 			len(s.StoragePaths), len(s.Integrations), len(s.PendingEvents))
@@ -218,27 +218,42 @@ func (s *Settings) migrateResticToRsync() {
 func (s *Settings) save() error {
 	data, err := json.MarshalIndent(s, "", "  ")
 	if err != nil {
+		if s.log != nil {
+			s.log.Printf("[ERROR] [settings] Failed to save: %v", err)
+		}
 		return fmt.Errorf("marshaling settings: %w", err)
 	}
 
 	tmpPath := s.path + ".tmp"
 	if err := os.MkdirAll(filepath.Dir(s.path), 0755); err != nil {
+		if s.log != nil {
+			s.log.Printf("[ERROR] [settings] Failed to save: %v", err)
+		}
 		return fmt.Errorf("creating settings dir: %w", err)
 	}
 
 	if err := os.WriteFile(tmpPath, data, 0644); err != nil {
 		os.Remove(tmpPath) // clean up partial file
+		if s.log != nil {
+			s.log.Printf("[ERROR] [settings] Failed to save: %v", err)
+		}
 		return fmt.Errorf("writing tmp settings: %w", err)
 	}
 
 	if err := os.Rename(tmpPath, s.path); err != nil {
 		os.Remove(tmpPath)
+		if s.log != nil {
+			s.log.Printf("[ERROR] [settings] Failed to save: %v", err)
+		}
 		return fmt.Errorf("renaming settings file: %w", err)
 	}
 
 	if s.debug {
 		s.log.Printf("[DEBUG] [settings] saved to %s (%d bytes)", s.path, len(data))
 	}
+	if s.log != nil {
+		s.log.Printf("[INFO] [settings] Settings saved")
+	}
 	return nil
 }
 
@@ -461,6 +476,9 @@ func (s *Settings) AddStoragePath(sp StoragePath) error {
 		}
 	}
 	s.StoragePaths = append(s.StoragePaths, sp)
+	if s.log != nil {
+		s.log.Printf("[INFO] [settings] Added storage path: %s", sp.Path)
+	}
 	return s.save()
 }
 
@@ -478,6 +496,9 @@ func (s *Settings) RemoveStoragePath(path string) error {
 		}
 	}
 	s.StoragePaths = kept
+	if s.log != nil {
+		s.log.Printf("[INFO] [settings] Removed storage path: %s", path)
+	}
 	return s.save()
 }
 
@@ -597,6 +618,9 @@ func (s *Settings) SetDisconnected(path string, disconnected bool, stoppedStacks
 	if s.debug {
 		s.log.Printf("[DEBUG] [settings] SetDisconnected path=%q disconnected=%v stopped_stacks=%d", path, disconnected, len(stoppedStacks))
 	}
+	if s.log != nil {
+		s.log.Printf("[INFO] [settings] Node disconnected: %v", disconnected)
+	}
 	for i := range s.StoragePaths {
 		if s.StoragePaths[i].Path == path {
 			s.StoragePaths[i].Disconnected = disconnected
@@ -707,6 +731,9 @@ func (s *Settings) SetDecommissioned(path, migratedTo string) error {
 	if s.debug {
 		s.log.Printf("[DEBUG] [settings] SetDecommissioned path=%q migrated_to=%q", path, migratedTo)
 	}
+	if s.log != nil {
+		s.log.Printf("[INFO] [settings] Node decommissioned")
+	}
 	for i := range s.StoragePaths {
 		if s.StoragePaths[i].Path == path {
 			s.StoragePaths[i].Decommissioned = true
@@ -842,6 +869,9 @@ func (s *Settings) AddPendingEvent(event PendingEvent) error {
 	if s.debug {
 		s.log.Printf("[DEBUG] [settings] AddPendingEvent type=%q severity=%q", event.EventType, event.Severity)
 	}
+	if s.log != nil {
+		s.log.Printf("[INFO] [settings] Added pending event: %s", event.EventType)
+	}
 	s.PendingEvents = append(s.PendingEvents, event)
 	return s.save()
 }