feat v1.25.0: three interaction modes — View / Plan / Devices (docs/UX-MODES.md)

- View (always the default): display + device interaction only; no dragging of
  icons/labels/openings; panning can start on an icon; clean header
- Plan: markup tools, openings editing (click-to-edit, drag along walls), label
  drag, space dialogs, fill palette; orange frame; icons hidden but labels visible
- Devices: icon drag only here, click opens the marker editor directly; add/
  show-all/reset/rules buttons; accent frame
- segmented mode control (admins only); removed: markup toggle button, view-mode
  opening drag/dblclick (v1.23.1), 'drag anywhere' (v1.9 reversed)
- README en+ru updated; TESTING.md Modes section; smoke_modes.mjs

src/i18n/ru.json

@@ -239,5 +239,8 @@
   "gs.reset": "Сбросить к умолчаниям",
   "gs.saved": "Общие настройки сохранены",
   "space.show_lqi": "Показывать зигби-сигнал (LQI) у устройств",
-  "gs.light_none": "Нет источников света"
+  "gs.light_none": "Нет источников света",
+  "mode.view": "Просмотр",
+  "mode.plan": "План",
+  "mode.devices": "Устройства"
 }