feat(profile): add learner public/private profile schema

[Ezeh20]

Summary

Closes #83

Adds a LearnerProfile model separate from User's private/account fields, with a modeled visibility system and tiered serializers.

• Schema: LearnerProfile (1:1 with User) — displayName, bio, avatarUrl, country, timezone, languages[], level, interests[], goals[], visibility. Indexed on country, level, visibility (the consented/searchable fields). Account status/verification remain on User, not duplicated here.

• Visibility: single ranked visibility field (private < employer < public, VISIBILITY_RANK in src/types/profile.types.ts)

• Serializers (src/services/profile-serializer.ts, pure functions, no I/O):

  • toOwnerProfile — full record + computed completion, always (ignores visibility — it's the owner's own view)
  • toEmployerProfile — full field set if visibility >= employer, else { id, visible: false }
  • toPublicProfile — narrower public-safe subset if visibility === public, else redacted
  • toPrivateProfile — internal-only; joins status/isVerified/phoneVerifiedAt from User. Never wired to a public or employer route.

  Verification evidence

• Schema: prisma/schema.prisma — LearnerProfile model.

• Migration: prisma/migrations/20260730120000_add_learner_profiles/migration.sql.

• Leakage tests: tests/profile-serializer.test.ts — redaction below each visibility tier, and explicit assertions that employer/public views never carry the private account fields.

• Service tests: tests/profile.service.test.ts — upsert defaults, partial updates, null-safe view fetching.

• Controller tests: tests/profile.controller.test.ts — auth gating, validation (closed schema, enum checks), owner/employer/public routing by caller identity.

• Privacy doc: docs/decisions/0002-learner-profile-visibility.md.

37 new tests added, full suite passing (475 passed, 3 pre-existing DB-integration tests skipped as before — unrelated to this change).