feat: Enhance users API with detailed response schemas and OpenAPI documentation

- Added response schemas for user operations including success and error responses.
- Updated existing routes to include OpenAPI schema definitions for better documentation.
- Implemented user statistics retrieval and role-based user listing with appropriate schemas.
- Improved error handling and response consistency across user-related endpoints.

Author: Lasim

.gitignore

@@ -67,3 +67,4 @@ services/backend/tests/e2e/test-data/*.db
 ._*.json
 cookies.txt
 cookiejar.txt
+services/backend/tests/e2e/.test-context.json