feat: add admin traffic usage page with TanStack Table

Add AdminTrafficUsage page showing per-user traffic statistics by node
with period filtering (1/3/7/14/30d), server-side sorting, search,
pagination, and CSV export. Uses @tanstack/react-table with manual
sorting and dynamic node columns.

package.json

@@ -32,6 +32,7 @@
     "@radix-ui/react-tooltip": "^1.2.8",
     "@radix-ui/react-visually-hidden": "^1.2.4",
     "@tanstack/react-query": "^5.8.0",
+    "@tanstack/react-table": "^8.21.3",
     "@telegram-apps/sdk-react": "^3.3.9",
     "autoprefixer": "^10.4.24",
     "axios": "^1.6.0",