fix: SyncFileBrowserMounts reads domain from controller config instead of missing .env

The filebrowser stack has no .env file — domain is baked into compose labels
by docker-setup.sh. The sync always bailed with a WARN and storage paths
were never applied to FileBrowser's config.yaml or docker-compose.yml.

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

controller/internal/web/handlers.go

@@ -1470,19 +1470,10 @@ func (s *Server) SyncFileBrowserMounts() {
 	// Get all active storage paths
 	paths := s.settings.GetStoragePaths()
 
-	// Read domain from .env
-	envPath := stackDir + "/.env"
-	domain := ""
-	if data, err := os.ReadFile(envPath); err == nil {
-		for _, line := range strings.Split(string(data), "\n") {
-			if strings.HasPrefix(line, "DOMAIN=") {
-				domain = strings.TrimPrefix(line, "DOMAIN=")
-				break
-			}
-		}
-	}
+	// Use domain from controller config
+	domain := s.cfg.Customer.Domain
 	if domain == "" {
-		s.logger.Printf("[WARN] Cannot read DOMAIN from FileBrowser .env — skipping mount sync")
+		s.logger.Printf("[WARN] Cannot sync FileBrowser mounts — customer domain not configured")
 		return
 	}