refactor(04-01): move API list test stubs into tests/ mirror dir to match convention

The two Wave-0 RED stubs (lists.test.ts, listEmitter.test.ts) were co-located in
src/ but all existing API tests live in apps/api/tests/. Move them to tests/routes/
and tests/lib/, add explicit vitest imports to match the tests/ convention, and
update path references in downstream plans 04-02..04-06. PWA tests keep co-location
(that IS the PWA convention).

apps/api/tests/lib/listEmitter.test.ts

@@ -9,6 +9,8 @@
  * Run: pnpm --filter @familysync/api test
  */
 
+import { describe, it } from 'vitest'
+
 describe('listEmitter — scoped fan-out correctness (D-04)', () => {
   it.todo('publishListEvent emits only to subscribers for the matching listId')
   it.todo('publishListEvent does NOT emit to subscribers for a different listId')

apps/api/tests/routes/lists.test.ts

@@ -10,6 +10,8 @@
  * Run: pnpm --filter @familysync/api test
  */
 
+import { describe, it } from 'vitest'
+
 describe('GET /api/lists — LIST-01: returns only accessible lists', () => {
   it.todo('returns empty array when user has no lists')
   it.todo('returns lists owned by the current user')