fix: prevent theme flash when navigating instance pages from hub iframe

Co-authored-by: Cursor <cursoragent@cursor.com>

manual_trading_hub/static/app.js

@@ -138,16 +138,19 @@
     shell.classList.remove("hidden");
     shell.setAttribute("aria-hidden", "false");
     document.body.classList.add("hub-instance-frame-open");
-    frame.addEventListener("load", function syncInstanceFrameTheme() {
-      try {
-        if (globalThis.HubTheme && typeof HubTheme.get === "function" && frame.contentWindow) {
-          frame.contentWindow.postMessage(
-            { type: "hub-theme-sync", theme: HubTheme.get() },
-            "*"
-          );
-        }
-      } catch (_) {}
-    });
+    if (frame.dataset.themeSyncBound !== "1") {
+      frame.dataset.themeSyncBound = "1";
+      frame.addEventListener("load", function syncInstanceFrameTheme() {
+        try {
+          if (globalThis.HubTheme && typeof HubTheme.get === "function" && frame.contentWindow) {
+            frame.contentWindow.postMessage(
+              { type: "hub-theme-sync", theme: HubTheme.get() },
+              "*"
+            );
+          }
+        } catch (_) {}
+      });
+    }
   }
 
   function closeInstanceFrame() {

manual_trading_hub/static/index.html

@@ -250,6 +250,6 @@
   <div id="toast"></div>
   <script src="https://unpkg.com/lightweight-charts@4.2.0/dist/lightweight-charts.standalone.production.js"></script>
   <script src="/assets/chart.js?v=20260604-upnl-contracts"></script>
-  <script src="/assets/app.js?v=20260604-risk-full-margin"></script>
+  <script src="/assets/app.js?v=20260604-iframe-theme-flash"></script>
 </body>
 </html>