Demo workflow: validate required fields before saving form data

[codingdud]

Purpose

Create a slightly broader issue for validating the full issue-delivery workflow.

Scope

• Add basic validation before saving form data
• Reject incomplete requests with a clear error response
• Keep the change aligned with the existing backend structure

Acceptance Criteria

• Requests with missing required fields are rejected
• Valid requests still save successfully
• The behavior is testable with a focused backend check