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

backend/app/templates/instance_detail.html

@@ -1460,12 +1460,17 @@ async function connectTerminal() {
             statusEl.style.color = 'var(--success)';
             terminalInstance.focus();
             
-            // Send initial resize
-            const dims = fitAddon.proposeDimensions();
-            if (dims) {
-                const resizeMsg = `1:${dims.cols}:${dims.rows}:`;
-                terminalWebSocket.send(resizeMsg);
-            }
+            // Send initial resize — fallback to 80x24 if proposeDimensions returns null
+            // (happens when xterm.css not loaded yet)
+            const sendResize = () => {
+                const dims = fitAddon.proposeDimensions();
+                const cols = dims ? dims.cols : 80;
+                const rows = dims ? dims.rows : 24;
+                terminalWebSocket.send(`1:${cols}:${rows}:`);
+            };
+            // Send immediately and re-send after layout settles
+            sendResize();
+            setTimeout(sendResize, 200);
         };
         
         terminalWebSocket.onmessage = (event) => {