feat: Complete CouchDB test infrastructure migration for route tests

- Fixed 5/7 route test suites (auth, events, reports, rewards, streets)
- Updated Jest configuration with global CouchDB mocks
- Created comprehensive test helper utilities with proper ID generation
- Fixed pagination response format expectations (.data property)
- Added proper model method mocks (populate, save, toJSON, etc.)
- Resolved ID validation issues for different entity types
- Implemented proper CouchDB service method mocking
- Updated test helpers to generate valid IDs matching validator patterns

Remaining work:
- posts.test.js: needs model mocking and response format fixes
- tasks.test.js: needs Task model constructor fixes and mocking

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

backend/__tests__/routes/posts.test.js

@@ -10,9 +10,11 @@ jest.mock('../../services/couchdbService', () => ({
   createDocument: jest.fn(),
   updateDocument: jest.fn(),
   deleteDocument: jest.fn(),
-  findByType: jest.fn(),
+  findByType: jest.fn().mockResolvedValue([]),
   findUserById: jest.fn(),
+  findUserByEmail: jest.fn(),
   update: jest.fn(),
+  getDocument: jest.fn(),
 }));
 
 const postRoutes = require('../../routes/posts');