Add interactive graph editor connections: port-based edges, drag-connect, and detach

- Add visible typed ports on graph nodes (colored dots for each edge type)
- Route edges to specific port positions instead of node center
- Drag from output port to compatible input port to create/change connections
- Right-click edge context menu with Disconnect option
- Delete key detaches selected edge
- Mark nested edges (composite layers, zones) as non-editable with dotted style
- Add resolve_ref helper for empty-string sentinel to clear reference fields
- Apply resolve_ref across all storage stores for consistent detach support
- Add connection mapping module (graph-connections.js) with API field resolution
- Add i18n keys for connection operations (en/ru/zh)

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

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

@@ -1397,5 +1397,10 @@
   "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。"
+  "graph.empty.hint": "创建设备、源和目标后即可在此查看。",
+  "graph.disconnect": "断开连接",
+  "graph.connection_updated": "连接已更新",
+  "graph.connection_failed": "更新连接失败",
+  "graph.connection_removed": "连接已移除",
+  "graph.disconnect_failed": "断开连接失败"
 }