fix: resolve test infrastructure issues

- Fixed server.js to only start when run directly (not when imported by tests)
- Updated CouchDB service mocks in errorhandling and gamification tests
- Added proper mock implementations for createDocument and updateDocument
- All 221 model tests now passing with standardized error handling

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

backend/__tests__/errorhandling.test.js

@@ -5,8 +5,14 @@ jest.mock('../services/couchdbService', () => ({
   create: jest.fn(),
   getById: jest.fn(),
   find: jest.fn(),
-  createDocument: jest.fn(),
-  updateDocument: jest.fn(),
+  createDocument: jest.fn().mockImplementation((doc) => ({
+    ...doc,
+    _rev: '1-abc123'
+  })),
+  updateDocument: jest.fn().mockImplementation((doc) => ({
+    ...doc,
+    _rev: '2-def456'
+  })),
   deleteDocument: jest.fn(),
   findByType: jest.fn().mockResolvedValue([]),
   findUserById: jest.fn(),