feat: multi-wallet architecture with localStorage state, EIP-712 verification, cross-tab WS leadership

- wallets.js: WalletManager state management with chain validation
- verifier.js: WalletVerifier EIP-712 signing via window.ethereum
- stream.js: WalletStreamManager with BroadcastChannel leader election, backoff + jitter
- AGENTS.md: updated with coding guidelines

default.conf

@@ -0,0 +1,12 @@
+server {
+    listen 80;
+    location / {
+        root /usr/share/nginx/html;
+        index index.html;
+    }
+    location /api/ {
+        proxy_pass http://192.168.1.102:8000/api/;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+    }
+}