fix: Use lowercase alphanumeric nanoid for Docker compose project names

Docker compose requires project names to be lowercase alphanumeric
with hyphens/underscores only. The default nanoid alphabet includes
uppercase and special characters, causing build failures.

apps/server/preview/manager.test.ts

@@ -67,7 +67,7 @@ vi.mock('node:fs/promises', () => ({
 }));
 
 vi.mock('nanoid', () => ({
-  nanoid: vi.fn(() => 'abc123test'),
+  customAlphabet: vi.fn(() => vi.fn(() => 'abc123test')),
 }));
 
 import { PreviewManager } from './manager.js';