v1.1.6: fix LXC xterm.js terminal (termproxy auth handshake)

- Add mandatory Proxmox termproxy auth: send 'USERNAME:VNCTICKET\n' as
  first WebSocket message, wait for 'OK' before starting PTY proxy
- Fix server.username → server.api_user (token suffix stripped)
- Fix CSRFPreventionToken sent in body → header only
- Fix additional_headers → extra_headers (websockets v12)
- Add URL-encoding for vncticket, PVEAuthCookie WS header, subprotocols=['binary']
- Forward initial terminal data arriving with OK frame
- Bump VERSION 1.1.5 → 1.1.6

nginx/conf.d/serverpanel.conf.template

@@ -66,8 +66,8 @@ server {
         proxy_read_timeout 60s;
     }
 
-    # WebSocket support (for future notifications)
-    location /ws {
+    # WebSocket support — tasks и terminal
+    location ~ ^/(ws|proxmox/ws)/ {
         proxy_pass http://serverpanel-app:8000;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
@@ -77,6 +77,7 @@ server {
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
         proxy_read_timeout 86400;
+        proxy_send_timeout 86400;
     }
 
     # API rate limiting (stricter)