feat: add fill+border dual-color nodes, radial layout, and dark labels

Node fill color now encodes subscription status (paid/trial active/expired),
while border color indicates referral role (partner/top/active referrer).
Added BFS-based radial initial positioning to spread referral branches outward.
Updated legend with two sections and adjusted FA2 gravity for less clustering.

package.json

@@ -31,6 +31,7 @@
     "@radix-ui/react-tabs": "^1.1.13",
     "@radix-ui/react-tooltip": "^1.2.8",
     "@radix-ui/react-visually-hidden": "^1.2.4",
+    "@sigma/node-border": "^3.0.0",
     "@tanstack/react-query": "^5.8.0",
     "@tanstack/react-table": "^8.21.3",
     "@telegram-apps/sdk-react": "^3.3.9",