feat: add D3.js network map visualization to Federation page

- Install d3@7 and @types/d3@7
- NetworkMap.vue: force-directed graph with draggable nodes, trust-level
  coloring (green/amber/red), online/offline opacity, dashed links
- Federation.vue: List/Map tab switcher with localStorage persistence
- Wire map to real federation data (self node centered, peers as satellites)
- Default to map view when 3+ nodes federated

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

neode-ui/package.json

@@ -23,6 +23,7 @@
     "generate-welcome-speech": "node scripts/generate-welcome-speech.js"
   },
   "dependencies": {
+    "d3": "^7.9.0",
     "dockerode": "^4.0.9",
     "fast-json-patch": "^3.1.1",
     "fuse.js": "^7.1.0",
@@ -33,6 +34,7 @@
   },
   "devDependencies": {
     "@playwright/test": "^1.58.2",
+    "@types/d3": "^7.4.3",
     "@types/node": "^24.10.0",
     "@vite-pwa/assets-generator": "^1.0.2",
     "@vitejs/plugin-vue": "^6.0.1",