feat: resolve Party Apple Music links with free iTunes lookup

[amitbreuer]

Summary

• Replace the Party Apple Music catalog API adapter with free public iTunes song lookup, removing paid Apple developer signing credentials from configuration and documentation.
• Update URL/catalog handling, trusted provider transport, error codes, frontend messages, and tests across affected surfaces.
• Preserve strict recording/version safety. Missing ISRC or incomplete identity evidence can require host selection rather than silent matching.
• Keep the same Brewtify app and bot; no standalone CLI, Docker, bot, schema or cloud changes in this PR.

Validation reported by implementation session

• All five workspace builds and 95 tests pass: 40 transport, 20 API, 17 native PostgreSQL, and 18 frontend.
• Focused lint passes.
• Two real read-only Israeli storefront iTunes lookups (Ensalada and Shivers) passed through the production adapter, with zero Spotify traffic.
• Browser validation is blocked: Chrome timeout/EPERM and cached Chromium SIGSEGV occurred before page loading. HTTP preview responds, but this is not browser-validation proof.

Limitations and release gates

• iTunes catalog coverage differs from Apple Music and does not provide ISRCs.
• No cache or application-wide iTunes quota enforcement was added; this remains a documented limitation. Explicit 429 responses use durable retry handling.
• No deployment, merge, cloud mutation or live enqueue was performed.
• Apple credentials are no longer a release gate. Remaining gates are Spotify callback/access, Party identity/allowlisting, Cloud Tasks/IAM/Scheduler, database baseline/migrations, and real Telegram/provider smoke verification.

Preview

http://127.0.0.1:5209/app/?section=party&demo=host (local development preview, not live service verification).