Add reject button for issue applications

[efstajas]

Summary

• Adds a "Reject" button on application cards and table rows for maintainers during active waves
• Opens a modal with an optional rejection reason field, informing the maintainer that the applicant will be notified and their quota freed
• Calls the new /api/wave-programs/{waveProgramId}/issues/{issueId}/applications/{applicationId}/reject endpoint with { rejectionReason } payload

Test plan

• As a maintainer, verify the "Reject" button appears on pending/unassigned applications during an active wave
• Verify the button does not appear when no active wave exists
• Click "Reject", confirm the modal shows with the correct description and optional reason field
• Submit with and without a reason, verify the application status updates to rejected
• Verify the applicant sees the rejected status on their application

[railway-app]

🚅 Deployed to the app-pr-1866 environment in Drips App

Service	Status	Web	Updated (UTC)
App	❌ Build Failed (View Logs)	Web	Mar 17, 2026 at 2:14 pm

4 services not affected by this PR

• Event Processor Jobs
• Search Sync
• Event Processor
• Fake Oracle API