fix(android): hydrate synced mobile lyrics

[grazzolini]

Summary

• Hydrate the current synced lyrics revision into mobile storage transactionally.
• Preserve transcript metadata, edits, segments, provenance, and timestamps without inventing data.
• Reconcile current, superseded, missing, and mobile-local lyrics without stale or destructive states.
• Match desktop manifest defaults and malformed-payload handling.
• Closes fix(android): hydrate synced analysis and timelines into mobile storage #332

Testing

• cd apps/desktop/src-tauri && cargo test mobile_backend --lib
• cd apps/desktop/src-tauri && cargo check
• cd apps/desktop/src-tauri && cargo fmt --all -- --check
• cd apps/backend && uv run --python 3.11 pytest tests/test_sync_manifest.py
• cd apps/backend && uv run --python 3.11 pytest tests/test_sync_revisions.py
• pnpm --filter @tuneforge/desktop lint
• pnpm --filter @tuneforge/desktop typecheck
• pnpm --filter @tuneforge/desktop test
• git diff --check
• Initial pnpm package:android:debug build and emulator deployment passed; the final rebuild was blocked before compilation by pnpm registry-signature release fetching.
• Android pairing and trust passed. Importer, storage, rendering, and restart persistence were validated; live sync stalled before manifest import, so end-to-end transport remains unverified.