fix(TestsPage): move lastActivityDate outside component to fix TDZ error

useMemo executes its factory immediately on first render. lastActivityDate
was defined with const after the useMemo call inside the component, causing
a temporal dead zone: 'Cannot access v before initialization'.

Fix: move the function to module scope (before the component), where it
is fully initialized before any hook runs.

frontend/src/pages/TestsPage.tsx

@@ -72,6 +72,23 @@ function currentTeamForState(state: TestState): string {
   }
 }
 
+/* ── Helper: most recent activity timestamp on a test ──────────────── */
+// updated_at column does not exist in the DB — derive from available fields
+function lastActivityDate(t: Test): string | null {
+  const candidates = [
+    t.blue_validated_at,
+    t.red_validated_at,
+    (t as any).blue_work_started_at,
+    (t as any).blue_started_at,
+    (t as any).red_started_at,
+    t.created_at,
+  ].filter(Boolean) as string[];
+  if (!candidates.length) return null;
+  return candidates.reduce((latest, d) =>
+    new Date(d) > new Date(latest) ? d : latest
+  );
+}
+
 /* ── Helper: elapsed time since a date ─────────────────────────────── */
 
 function formatElapsed(dateStr: string | null | undefined): string {
@@ -281,23 +298,6 @@ export default function TestsPage() {
     });
   };
 
-  // updated_at doesn't exist in DB — derive "last activity" from the most
-  // recent non-null timestamp available on the test record
-  const lastActivityDate = (t: import("../types/models").Test): string | null => {
-    const candidates = [
-      t.blue_validated_at,
-      t.red_validated_at,
-      (t as any).blue_work_started_at,
-      (t as any).blue_started_at,
-      (t as any).red_started_at,
-      t.created_at,
-    ].filter(Boolean) as string[];
-    if (!candidates.length) return null;
-    return candidates.reduce((latest, d) =>
-      new Date(d) > new Date(latest) ? d : latest
-    );
-  };
-
   // ── My tasks label ────────────────────────────────────────────────
   const myTasksLabel = useMemo(() => {
     if (!user) return "My Tasks";