feat: Admin APIs for manual mentor assignment and confirming no match found

[womencodingcommunity]

Context

Once a mentee is in PENDING_MANUAL_MATCH, admins have two options:

1. Manually assign a mentor — admin finds a suitable mentor outside the original priority list and creates a new application
2. Confirm no match found — after exhausting all manual options, admin marks the mentee as unmatched for this cycle

Changes Required

MenteeWorkflowService

• Add assignMentor(menteeId, cycleId, mentorId, notes):
  • Validates mentor exists and has capacity
  • Closes the PENDING_MANUAL_MATCH placeholder application
  • Creates a new MenteeApplication for the mentee→mentor pairing with status PENDING
  • Normal acceptance flow continues from there
• Add confirmNoMatch(menteeId, cycleId, reason):
  • Sets NO_MATCH_FOUND on the PENDING_MANUAL_MATCH placeholder application
  • Terminal — no further actions possible for this mentee in this cycle

New API endpoints

POST /api/platform/v1/mentees/{menteeId}/cycles/{cycleId}/assign-mentor
Body: { "mentorId": number, "notes": "string" }
Response: Newly created MenteeApplication

POST /api/platform/v1/mentees/{menteeId}/cycles/{cycleId}/no-match
Body: { "reason": "string" }
Response: Updated MenteeApplication

Acceptance Criteria

• assignMentor() creates new application and closes placeholder
• Mentor capacity validated before assignment
• confirmNoMatch() sets NO_MATCH_FOUND and is terminal
• Both endpoints require admin permission and documented in OpenAPI/Swagger
• Unit and integration tests

Dependencies

• Ticket: feat: Auto-detect exhausted priorities and transition to PENDING_MANUAL_MATCH