Restore nest coverage to >=80% after the #1209 dep bump (istanbul provider + branch tests) (#1213)

* fix(server): set oxc:false in vitest so the SWC transform survives the Vite 8 bump

* fix(server): switch coverage to the istanbul provider (v8 under-reports branches on Vite 8 + Vitest 4)

* test(nest): cover controller/service branches to clear the 80% coverage gate

server/tests/unit/nest/addons.controller.test.ts

@@ -0,0 +1,26 @@
+import { describe, it, expect, vi } from 'vitest';
+import { AddonsController } from '../../../src/nest/addons/addons.controller';
+import type { AddonsService } from '../../../src/nest/addons/addons.service';
+
+function makeService(overrides: Partial<AddonsService> = {}): AddonsService {
+  return {
+    list: vi.fn().mockReturnValue({ collabFeatures: {}, bagTracking: false, addons: [] }),
+    ...overrides,
+  } as unknown as AddonsService;
+}
+
+describe('AddonsController (parity with the legacy GET /api/addons route)', () => {
+  it('GET / delegates straight to the service and returns its feed', () => {
+    const feed = {
+      collabFeatures: { comments: true },
+      bagTracking: true,
+      addons: [{ id: 'atlas', name: 'Atlas', type: 'page', icon: 'globe', enabled: true }],
+    };
+    const list = vi.fn().mockReturnValue(feed);
+    const svc = makeService({ list } as Partial<AddonsService>);
+
+    expect(new AddonsController(svc).list()).toBe(feed);
+    expect(list).toHaveBeenCalledTimes(1);
+    expect(list).toHaveBeenCalledWith();
+  });
+});