fix(user-profile): migrate to Coves lexicon with OAuth DPoP improvements master
Migrate user profile handling from app.bsky.actor.profile to the Coves-specific social.coves.actor.profile lexicon, and improve the OAuth authentication flow with proper DPoP token handling. Changes: - Migrate profile collection from app.bsky.actor.profile to social.coves.actor.profile - Refactor UpdateProfileHandler to use pds.Client interface with DPoP auth - Add PDSClientFactory for dependency injection (enables password auth in E2E tests) - Add ErrRateLimited (429) and ErrPayloadTooLarge (413) error handling - Update Jetstream consumer and config to filter on Coves profile collection - Add constructor validation with panic on nil dependencies - Add 15+ new tests: nil handling, boundary conditions, error paths - Refactor tests to use mock pds.Client instead of HTTP roundtrippers - Fix logging levels for Jetstream consumer (nil data → WARN, cache purge → ERROR) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>