fix(tests): move showTemplateModal useState before early returns (React #310)

The useState hook was placed after the isLoading/error early returns,
violating the Rules of Hooks. First render hit the early return without
calling the hook; second render (after data loaded) called it, producing
'more hooks than previous render' — React error #310 and a white screen.

Moved const [showTemplateModal] to the state block at the top of the
component, alongside the other useState declarations.

frontend/src/pages/TestDetailPage.tsx

@@ -65,6 +65,7 @@ export default function TestDetailPage() {
   });
 
   const [toast, setToast] = useState<{ message: string; type: "success" | "error" } | null>(null);
+  const [showTemplateModal, setShowTemplateModal] = useState(false);
 
   // ── Queries ────────────────────────────────────────────────────
 
@@ -366,8 +367,6 @@ export default function TestDetailPage() {
   const canSaveAsTemplate =
     role === "red_lead" || role === "blue_lead" || role === "admin";
 
-  const [showTemplateModal, setShowTemplateModal] = useState(false);
-
   // ── Render ─────────────────────────────────────────────────────
 
   return (