TEST: Mentor registration

[nora-weisser]

• POST /api/platform/v1/mentors is anonymous. The server always sets profileStatus = PENDING regardless of input.
• Re-registering with an email already tied to a member reuses that member.id and re-issues a PENDING status. No duplicate member row is created.
• Calendly link is required at registration (per PM); validate URL format. Missing or malformed → 4xx.
• Cycle preference combinations accepted at registration:
  • longTerm populated only → long-term only.
  • adHoc non-empty only → ad-hoc only.
  • Both populated → both.
• Long-term commitment validation: LongTermMentorship.hours / numMentee >= 2. Submissions with hoursPerMentee < 2 are rejected with IllegalArgumentException from MentorshipService.validateMentorCommitment.
• PATCH /mentors/{id}/accept (permission MENTOR_APPROVE) transitions to ACTIVE and sends the approval email. Calling on an already-active mentor → MentorStatusException.
• PATCH /mentors/{id}/reject (permission MENTOR_APPROVE) requires a reason in the body; transitions to REJECTED and sends the rejection email. Calling on an already-rejected mentor → MentorStatusException.
• After accept, mentor appears on the website and is selectable in the list in mentee registration.
• After reject, mentor does not appear in the website.