Add basic MEAD artist profile updates

[raymondjacobson]

Summary

• parse MEAD artist profile updates for display name, bio, profile image, and cover art
• persist MEAD updates in a dedicated artist_profile_updates queue with pending/blocked/failed/published states
• apply pending artist profile updates through sdk.users.updateUser before release publishing
• add fixture and example-style tests showing standalone MeadMessage, Feed/Entry by Audius handle, and blocked unmatched artist payloads

Test plan

• npm run tsc
• DB_URL=postgresql://postgres:test@127.0.0.1:40111/ddex_mead_test npx vitest run src/parseMead.test.ts
• DB_URL=postgresql://postgres:test@127.0.0.1:40111/ddex_mead_test npm test