Add visual graph editor for entity interconnections

SVG-based node graph with ELK.js autolayout showing all 13 entity types
and their relationships. Features include:

- Pan/zoom canvas with bounds clamping and dead-zone click detection
- Interactive minimap with viewport rectangle, click-to-pan, drag-to-move,
  and dual resize handles (bottom-left/bottom-right)
- Movable toolbar with drag handle and inline zoom percentage indicator
- Entity-type SVG icons from Lucide icon set with subtype-specific overrides
- Command palette search (/) with keyboard navigation and fly-to
- Node selection with upstream/downstream chain highlighting
- Double-click to zoom-to-card, edit/delete overlay on hover
- Legend panel, orphan node detection, running state indicators
- Full i18n support with languageChanged re-render
- Catmull-Rom-to-cubic bezier edge routing for smooth curves

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

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

@@ -1373,5 +1373,16 @@
   "sync_clock.reset_done": "时钟已重置为零",
   "sync_clock.delete.confirm": "删除此同步时钟？关联的源将失去同步并以默认速度运行。",
   "color_strip.clock": "同步时钟：",
-  "color_strip.clock.hint": "关联同步时钟以在多个源之间同步动画。速度在时钟上控制。"
+  "color_strip.clock.hint": "关联同步时钟以在多个源之间同步动画。速度在时钟上控制。",
+  "graph.title": "图表",
+  "graph.fit_all": "显示所有节点",
+  "graph.zoom_in": "放大",
+  "graph.zoom_out": "缩小",
+  "graph.search": "搜索节点",
+  "graph.search_placeholder": "搜索实体...",
+  "graph.legend": "图例",
+  "graph.minimap": "小地图",
+  "graph.relayout": "重新布局",
+  "graph.empty": "暂无实体",
+  "graph.empty.hint": "创建设备、源和目标后即可在此查看。"
 }