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/web/handler_export.go

@@ -109,6 +109,7 @@ func (s *Server) apiExportEstimate(w http.ResponseWriter, r *http.Request) {
 
 	est, err := s.appExporter.EstimateExport(stackName, drive)
 	if err != nil {
+		s.logger.Printf("[ERROR] [web] Export estimate failed for %s: %v", stackName, err)
 		s.logger.Printf("[DEBUG] [handler_export] apiExportEstimate error: %v", err)
 		jsonError(w, err.Error(), http.StatusInternalServerError)
 		return
@@ -162,6 +163,7 @@ func (s *Server) apiExportStart(w http.ResponseWriter, r *http.Request) {
 		StopApp:   req.StopApp,
 	})
 	if err != nil {
+		s.logger.Printf("[ERROR] [web] Export start failed for %s: %v", req.StackName, err)
 		s.logger.Printf("[DEBUG] [handler_export] apiExportStart error: %v", err)
 		jsonError(w, err.Error(), http.StatusConflict)
 		return
@@ -306,6 +308,7 @@ func (s *Server) apiImportStart(w http.ResponseWriter, r *http.Request) {
 		Password: req.Password,
 	})
 	if err != nil {
+		s.logger.Printf("[ERROR] [web] Import start failed for %s: %v", req.Path, err)
 		s.logger.Printf("[DEBUG] [handler_export] apiImportStart error: %v", err)
 		jsonError(w, err.Error(), http.StatusConflict)
 		return