fix(web): update setupSuccessfulFetch type to include replyCount and lastReplyAt

The helper's topics array element type was not updated alongside makeTopicsResponse,
causing tsc to reject the new test cases with TS2353. Vitest strips types via esbuild
so it passed locally; tsc in CI caught the mismatch.

apps/web/src/routes/__tests__/boards.test.tsx

···
    *   3 (sequential): GET /api/categories/7
    */
   function setupSuccessfulFetch(options: {
-    topics?: Array<{ id?: string; did?: string; handle?: string | null; text?: string; createdAt?: string }>;
+    topics?: Array<{ id?: string; did?: string; handle?: string | null; text?: string; createdAt?: string; replyCount?: number; lastReplyAt?: string | null }>;
     total?: number;
     offset?: number;
     boardOverrides?: Partial<Record<string, unknown>>;