Standardise JSON response structure for actions

### Description

Currently, actions construct JSON responses in an inconsistent way, leading to duplication and potential variation in response formats.

Introduce a standardised approach for returning JSON responses from actions to ensure:

- Consistent structure across all endpoints
- Reduced boilerplate in individual actions
- Easier maintenance and evolution of response format

### Acceptance Criteria

- Actions return responses in a consistent JSON structure
- Response creation logic is centralised
- Existing actions are updated to follow the new approach

### Notes

- Implementation approach is open (helper methods, service, responder, etc.)
- Should support both success and error responses