Add event-prefixed ticket numbers generated on confirmation

[barakadanny]

Description

Ticket numbers now carry an event prefix (e.g. AFRI-T4R2B) and are assigned only when payment is confirmed, not at purchase

Type of change

• Chore (maintenance work, dependency updates)
• Refactor (restructuring existing implementation, no behavior change)
• New feature (adds functionality)
• Bug fix (fixes an issue)
• Add tests (test-related changes only)

Related issues

Fix #

Breaking changes

• This PR introduces a breaking change

If checked, describe what breaks and how consumers should migrate.

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows the platform security practices and guidelines

Screenshots (if applicable)

Attach screenshots or screen recordings for any UI changes. Write N/A if not applicable.