test: MVP-4 Sprint 4 - Version history tests

- Add 11 tests for versions.ts (create, get, restore, edge cases)
- Add noteVersion mock to api.integration.test.ts

__tests__/api.integration.test.ts

@@ -38,6 +38,11 @@ const mockPrisma = {
     create: jest.fn(),
     createMany: jest.fn(),
   },
+  noteVersion: {
+    create: jest.fn(),
+    findMany: jest.fn(),
+    findUnique: jest.fn(),
+  },
   $transaction: jest.fn((callback) => callback(mockPrisma)),
 }