Manage several servers from one panel: core + nodes

A node is a VPN server without a panel. awg-agent on it dials the panel
(core) over an outbound WSS connection and runs the panel's requests on its
own awg-ctrl, which stays on 127.0.0.1 and is unchanged. No inbound port on
the node, works behind NAT.

- awg-ui/nodes.ts: node registry in ui.db, WSS hub on NODE_PORT with a
  self-signed cert whose SPKI pin goes into the join string, RPC with
  timeouts, health polling, /ui/nodes routes.
- Nodes enroll with a one-time awgjoin:// string (secret stored hashed,
  1 hour) and then authenticate by their own Ed25519 key. The agent checks
  the pin before sending anything and only forwards /health, /api/*, /awg/*.
- server_id 0 is the panel's own awg-ctrl; LOCAL_NODE=off makes the panel
  run without a VPN of its own. The panel picks a server with X-Server-Id,
  API keys use their server_id. sen:// still serves one server.
- UI: a card per server in the server bar, switching remounts the tab,
  «Добавить сервер» gives the join command.
- CLI: agent service, roles from cli.env, join / unjoin commands.
- Release archives include awg-agent.

awg-ui/package.json

@@ -15,20 +15,22 @@
     "better-sqlite3": "^12.10.0",
     "qrcode": "^1.5.0",
     "react": "^18.3.0",
-    "react-dom": "^18.3.0"
+    "react-dom": "^18.3.0",
+    "ws": "^8.22.0"
   },
   "devDependencies": {
-    "concurrently": "^9.0.0",
     "@types/better-sqlite3": "^7.6.13",
-    "@types/qrcode": "^1.5.0",
     "@types/express": "^4.17.0",
     "@types/node": "^22.0.0",
+    "@types/qrcode": "^1.5.0",
     "@types/react": "^18.3.0",
     "@types/react-dom": "^18.3.0",
+    "@types/ws": "^8.18.1",
     "@vitejs/plugin-react": "^4.3.0",
+    "concurrently": "^9.0.0",
     "express": "^4.19.0",
     "tsx": "^4.7.0",
     "typescript": "^5.4.0",
     "vite": "^5.4.0"
   }
-}
+}