feat: rewrite sankey chart with D3 — thin bars, labels beside nodes, proper hover

Replace @nivo/sankey with custom D3 implementation:
- 30px thin node bars with labels positioned beside them
- Links at 0.3 opacity, 0.6 on hover with full path highlighting
- Colors based on first URL segment for visual grouping
- Dynamic height based on tallest column
- Responsive width via ResizeObserver
- Click nodes to filter, hover for tooltips
- Invisible wider hit areas for easier link hovering
- Remove @nivo/sankey dependency, add d3

package.json

@@ -14,15 +14,16 @@
   "dependencies": {
     "@ciphera-net/ui": "^0.2.7",
     "@ducanh2912/next-pwa": "^10.2.9",
-    "@nivo/sankey": "^0.99.0",
     "@phosphor-icons/react": "^2.1.10",
     "@simplewebauthn/browser": "^13.2.2",
     "@stripe/react-stripe-js": "^5.6.0",
     "@stripe/stripe-js": "^8.7.0",
     "@tanstack/react-virtual": "^3.13.21",
+    "@types/d3": "^7.4.3",
     "class-variance-authority": "^0.7.1",
     "cobe": "^0.6.5",
     "country-flag-icons": "^1.6.4",
+    "d3": "^7.9.0",
     "d3-scale": "^4.0.2",
     "framer-motion": "^12.23.26",
     "html-to-image": "^1.11.13",