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/en.json

@@ -1373,5 +1373,16 @@
   "sync_clock.reset_done": "Clock reset to zero",
   "sync_clock.delete.confirm": "Delete this sync clock? Linked sources will lose synchronization and run at default speed.",
   "color_strip.clock": "Sync Clock:",
-  "color_strip.clock.hint": "Link to a sync clock to synchronize animation timing across sources. Speed is controlled on the clock."
+  "color_strip.clock.hint": "Link to a sync clock to synchronize animation timing across sources. Speed is controlled on the clock.",
+  "graph.title": "Graph",
+  "graph.fit_all": "Fit all nodes",
+  "graph.zoom_in": "Zoom in",
+  "graph.zoom_out": "Zoom out",
+  "graph.search": "Search nodes",
+  "graph.search_placeholder": "Search entities...",
+  "graph.legend": "Legend",
+  "graph.minimap": "Minimap",
+  "graph.relayout": "Re-layout",
+  "graph.empty": "No entities yet",
+  "graph.empty.hint": "Create devices, sources, and targets to see them here."
 }