feat: add Relations tab with force-directed resource dependency graph (#96)

Add a new "Relations" tab after "Images" that visualizes resource
dependencies within a Helm release as an interactive force-directed graph.
Detects relationships via ownerReferences, *Ref fields, volumes, env refs,
service selectors, ingress backends, and RBAC bindings. External resources
appear as dashed oval ghost nodes. Color-coded by resource category.

Closes #96

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -24,8 +24,12 @@
     "cypress:component:open": "cypress open --component"
   },
   "dependencies": {
+    "@dagrejs/dagre": "^2.0.4",
     "@tanstack/react-query": "^5.90.21",
+    "@types/d3-force": "^3.0.10",
+    "@xyflow/react": "^12.10.1",
     "compare-versions": "^6.1.1",
+    "d3-force": "^3.0.0",
     "diff2html": "^3.4.52",
     "flowbite-react": "^0.12.17",
     "highlight.js": "^11.11.1",