fix: wrap custom script execution in try-catch to prevent ReferenceError

Fixes FORMBRICKS-TK

Custom scripts injected via CustomScriptsInjector can attempt to access
undefined global variables (like zp_token) before they're defined, causing
a ReferenceError that breaks the survey page.

This fix wraps inline script content in an IIFE with try-catch to gracefully
handle errors from undefined variables. Also adds error handlers for external
scripts that fail to load.

The survey page will now continue to function even when custom scripts
encounter runtime errors, with warnings logged to the console for debugging.

apps/web/modules/survey/link/components/custom-scripts-injector.tsx

@@ -56,11 +56,26 @@ export const CustomScriptsInjector = ({
           newScript.setAttribute(attr.name, attr.value);
         });
 
-        // Copy inline script content
+        // Copy inline script content with error handling
         if (script.textContent) {
-          newScript.textContent = script.textContent;
+          // Wrap inline scripts in try-catch to prevent undefined variable errors
+          const wrappedContent = `
+(function() {
+  try {
+${script.textContent}
+  } catch (error) {
+    console.warn("[Formbricks] Custom script error:", error);
+  }
+})();
+`;
+          newScript.textContent = wrappedContent;
         }
 
+        // Add error handler for external scripts
+        newScript.onerror = (error) => {
+          console.warn("[Formbricks] Custom script failed to load:", error);
+        };
+
         document.head.appendChild(newScript);
       });