B1: migrate UI wiring — /api/storage/migrate{,-app,/status} + settings & app pages

ServeStorageAPI gains POST /api/storage/migrate (whole-namespace), POST
/api/storage/migrate-app (single app), GET /api/storage/migrate/status (poll).
settings.html: the greyed migrate-all span becomes a real target-select + button +
shared progress panel; app_info.html gains a per-app 'Áthelyezés másik tárhelyre'
control. Both poll the shared status endpoint and render Hungarian phase progress.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

controller/internal/web/storage_handlers.go

@@ -245,11 +245,61 @@ func (s *Server) ServeStorageAPI(w http.ResponseWriter, r *http.Request) {
 		s.handleStorageRegister(w, r)
 	case r.URL.Path == "/api/storage/activate" && r.Method == http.MethodPost:
 		s.handleStorageActivate(w, r)
+	case r.URL.Path == "/api/storage/migrate" && r.Method == http.MethodPost:
+		s.handleStorageMigrate(w, r)
+	case r.URL.Path == "/api/storage/migrate-app" && r.Method == http.MethodPost:
+		s.handleStorageMigrateApp(w, r)
+	case r.URL.Path == "/api/storage/migrate/status" && r.Method == http.MethodGet:
+		s.handleStorageMigrateStatus(w, r)
 	default:
 		http.NotFound(w, r)
 	}
 }
 
+// handleStorageMigrate starts a whole-namespace migration (all apps + non-app content) off the source
+// drive onto the chosen target. Async: VALIDATE runs synchronously (a refusal is returned here and
+// changes nothing); the copy/redeploy/cleanup run in the background and the UI polls migrate/status.
+func (s *Server) handleStorageMigrate(w http.ResponseWriter, r *http.Request) {
+	var req struct {
+		Source string `json:"source"`
+		Target string `json:"target"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeDiskJSON(w, http.StatusBadRequest, false, "érvénytelen kérés", nil)
+		return
+	}
+	id, err := s.stackMgr.MigrateAll(r.Context(), strings.TrimSpace(req.Source), strings.TrimSpace(req.Target))
+	if err != nil {
+		writeDiskJSON(w, http.StatusConflict, false, err.Error(), nil)
+		return
+	}
+	writeDiskJSON(w, http.StatusOK, true, "", map[string]any{"started": true, "id": id})
+}
+
+// handleStorageMigrateApp starts a single-app migration onto the chosen target.
+func (s *Server) handleStorageMigrateApp(w http.ResponseWriter, r *http.Request) {
+	var req struct {
+		App    string `json:"app"`
+		Target string `json:"target"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeDiskJSON(w, http.StatusBadRequest, false, "érvénytelen kérés", nil)
+		return
+	}
+	id, err := s.stackMgr.MigrateApp(r.Context(), strings.TrimSpace(req.App), strings.TrimSpace(req.Target))
+	if err != nil {
+		writeDiskJSON(w, http.StatusConflict, false, err.Error(), nil)
+		return
+	}
+	writeDiskJSON(w, http.StatusOK, true, "", map[string]any{"started": true, "id": id})
+}
+
+// handleStorageMigrateStatus returns the live migration job (nil/idle when none is running) for the
+// progress panel poll.
+func (s *Server) handleStorageMigrateStatus(w http.ResponseWriter, r *http.Request) {
+	writeDiskJSON(w, http.StatusOK, true, "", map[string]any{"job": s.stackMgr.MigrationStatus()})
+}
+
 type storageProvReq struct {
 	Device     string `json:"device"`
 	FSType     string `json:"fstype"`