Address review: remove fallback route, handle trailing splat, extract shared path

- Remove the path="*" fallback Route so mismatches between mountPath
  and initialRouteEntries surface as test failures instead of silently
  rendering without params
- Handle mountPath values that already end with /* to avoid double splat
- Extract repeated entity path string into a shared constant

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Fredrik Adelöw <freben@gmail.com>

packages/frontend-test-utils/src/app/renderInTestApp.tsx

@@ -157,11 +157,12 @@ export function renderInTestApp<const TApiPairs extends any[] = any[]>(
 
         if (mountPath) {
           const routePath =
-            mountPath === '/' ? mountPath : `${mountPath.replace(/\/$/, '')}/*`;
+            mountPath === '/' || mountPath.endsWith('/*')
+              ? mountPath
+              : `${mountPath.replace(/\/$/, '')}/*`;
           content = (
             <Routes>
               <Route path={routePath} element={content} />
-              <Route path="*" element={content} />
             </Routes>
           );
         }