Mentorship: mentor directory endpoints (Phase 6.6 backend)

[pablo-clueless]

Scope

Public-to-members directory the frontend grid consumes.

Method	Path	Auth	Notes
GET	/mentorship/mentors	active member	paginated; filters: expertiseTag, acceptingOnly=true
GET	/mentorship/mentors/{id}	active member	mentor detail incl. expertise, capacity headroom, availability summary

Rules

• Enrich with member card data (display name, title, avatar) via the Members module public contract — no cross-module DbContext reach-ins.
• Exclude mentors whose underlying member is not Active (pending/deactivated must never surface — query level, not UI level).
• acceptingOnly filters on IsAcceptingMentees and actual capacity headroom (belt and braces — the flag can lag).
• Detail endpoint exposes weekly availability in the mentor's timezone plus the IANA id, so the booking UI can convert client-side.

Error codes

mentorship.not_found

Dependencies

Blocked by #9. Capacity headroom needs #10's Mentorship table (soft — can land computing headroom as capacity until M2 merges).

Acceptance criteria

• Deactivated/pending members filtered out (tested)
• Tag filter matches case-insensitively
• Pagination + deterministic ordering (accepting first, then newest opt-in)

Conventions (project-wide, non-negotiable)

• .NET 9, records for immutable shapes, file-scoped namespaces, primary constructors where they read well. Minimal-API endpoints grouped per module via IEndpointModule.MapEndpoints.
• Result<T> (SharedKernel) instead of exception-driven control flow. Endpoint results map failures to ProblemDetails with the stable error codes listed above — the frontend keys off them.
• Module owns its EF Core DbContext mapped to its own Postgres schema. Modules never reference each other's internals — cross-module needs go through a public contract interface or an in-process domain event (IEventPublisher).
• All external calls (GitHub, Stripe, Brevo, Cloudinary, Meilisearch) behind interfaces owned by the consuming module.
• Every list endpoint paginated (offset is fine). xUnit tests in tests/CommunityPro.Tests/<Module>/ following the existing harness patterns (see Members/MembersTestHarness.cs).