Add graph editor filter, anchor-based positioning, and context docs

- Add name/kind/subtype filter bar with keyboard shortcut (F key)
- Filtered-out nodes get dimmed styling, nearly invisible on minimap
- Add anchor-based positioning for minimap and toolbar (remembers
  which corner element is closest to, maintains offset on resize)
- Fix minimap not movable after reload (_applyMinimapAnchor undefined)
- Fix ResizeObserver to use anchor system for both minimap and toolbar
- Add graph-editor.md context file and update frontend.md with graph sync notes
- Add filter i18n keys for en/ru/zh locales

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

server/src/wled_controller/static/locales/ru.json

@@ -1407,5 +1407,8 @@
   "graph.relayout_confirm": "Сбросить все ручные позиции узлов и перестроить граф?",
   "graph.fullscreen": "Полноэкранный режим",
   "graph.add_entity": "Добавить сущность",
-  "graph.color_picker": "Цвет узла"
+  "graph.color_picker": "Цвет узла",
+  "graph.filter": "Фильтр узлов",
+  "graph.filter_placeholder": "Фильтр по имени...",
+  "graph.filter_clear": "Очистить фильтр"
 }