feat: comprehensive debug logging across all controller modules

Add detailed [DEBUG] logging to every controller module when
logging.level is set to "debug". Each module with stateful debug
uses SetDebug(bool) wired from main.go. Covers stacks, backup,
cloudflare, integrations, system, monitor, settings, scheduler,
web handlers, storage, metrics, API, selfupdate, and assets.

Also includes the app export/import (.fab bundles) feature from
v0.32.0 and its debug page integration.

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

controller/internal/backup/restore_scan.go

@@ -163,6 +163,9 @@ func ScanDrivesForBackups(mountedPaths []string, stacks []InfraStackInfo, logger
 		Status: "pending",
 	}
 
+	logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: scanning %d mount paths, %d stacks from manifest",
+		len(mountedPaths), len(stacks))
+
 	// Build drive info and find backup directories
 	type driveBackup struct {
 		drivePath string
@@ -181,6 +184,8 @@ func ScanDrivesForBackups(mountedPaths []string, stacks []InfraStackInfo, logger
 			Available: avail,
 		}
 
+		logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: checking drive %s (label=%s, available=%v)", mp, label, avail)
+
 		secPath := SecondaryBackupPath(mp)
 		if dirExists(secPath) {
 			di.HasBackup = true
@@ -195,6 +200,8 @@ func ScanDrivesForBackups(mountedPaths []string, stacks []InfraStackInfo, logger
 		plan.Drives = append(plan.Drives, di)
 	}
 
+	logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: found %d drives with backup data", len(backupDrives))
+
 	// For each stack from the manifest, look for backup data on drives
 	for _, stack := range stacks {
 		app := RestorableApp{
@@ -205,12 +212,16 @@ func ScanDrivesForBackups(mountedPaths []string, stacks []InfraStackInfo, logger
 			Status:      "pending",
 		}
 
+		logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: scanning for app %s (needsHDD=%v, hddPath=%s)",
+			stack.Name, stack.NeedsHDD, stack.HDDPath)
+
 		// Check if app data exists directly on HDD (common case: HDD survived)
 		if stack.HDDPath != "" {
 			dataDir := AppDataDir(stack.HDDPath, stack.Name)
 			if dirExists(dataDir) {
 				app.HasData = true
 				app.DataPath = dataDir
+				logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: %s — live data found at %s", stack.Name, dataDir)
 			}
 		}
 
@@ -224,6 +235,8 @@ func ScanDrivesForBackups(mountedPaths []string, stacks []InfraStackInfo, logger
 			// Found a backup for this app
 			app.DrivePath = db.drivePath
 			app.DriveLabel = db.label
+			logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: %s — backup found on drive %s at %s",
+				stack.Name, db.label, rsyncBase)
 
 			// Check for _config/ (stack compose directory backup)
 			configDir := filepath.Join(rsyncBase, "_config")
@@ -245,6 +258,9 @@ func ScanDrivesForBackups(mountedPaths []string, stacks []InfraStackInfo, logger
 				app.RsyncDataPath = rsyncBase
 			}
 
+			logger.Printf("[DEBUG] [backup] ScanDrivesForBackups: %s — config=%v, dbDump=%v, rsyncData=%v",
+				stack.Name, app.HasConfig, app.HasDBDump, app.HasRsyncData)
+
 			break // use first drive with backup for this app
 		}