fix(backend): saved-views DELETE 204 response + add route test

- DELETE /saved-views/:id now uses reply.code(204).send() for explicit
  empty response (Fastify 5 best practice)
- Added routes.test.ts for saved-views module (verifies 2 GET, 1 POST,
  1 PATCH, 1 DELETE handler registration)
- Backend now at 19 tests across 11 files

backend/src/modules/saved-views/routes.test.ts

@@ -0,0 +1,38 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { savedViewRoutes } from './routes.js';
+
+const { extractAuthMock } = vi.hoisted(() => ({
+  extractAuthMock: vi.fn(async () => ({ sub: 'user_1' })),
+}));
+
+vi.mock('../../lib/auth.js', () => ({ extractAuth: extractAuthMock }));
+vi.mock('../../lib/product-config.js', () => ({ PRODUCT_ID: 'notelett' }));
+vi.mock('./repository.js', () => ({
+  listSavedViews: vi.fn(async () => ({ items: [], total: 0 })),
+  getSavedView: vi.fn(async () => null),
+  createSavedView: vi.fn(async (doc: unknown) => doc),
+  updateSavedView: vi.fn(async () => null),
+  deleteSavedView: vi.fn(async () => false),
+}));
+
+describe('savedViewRoutes', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('registers route handlers', async () => {
+    const app = {
+      get: vi.fn(),
+      post: vi.fn(),
+      patch: vi.fn(),
+      delete: vi.fn(),
+    };
+
+    await savedViewRoutes(app as never);
+
+    expect(app.get).toHaveBeenCalledTimes(2);
+    expect(app.post).toHaveBeenCalledTimes(1);
+    expect(app.patch).toHaveBeenCalledTimes(1);
+    expect(app.delete).toHaveBeenCalledTimes(1);
+  });
+});

backend/src/modules/saved-views/routes.ts

@@ -104,7 +104,6 @@ export async function savedViewRoutes(app: FastifyInstance) {
       throw new NotFoundError('Saved view not found');
     }
 
-    reply.code(204);
-    return;
+    reply.code(204).send();
   });
 }