feat(node): Music app node-side — indexing, MusicBrainz enrichment, protocol

Implements the node half of docs/musicbay.md against MNP 0.8:

- IndexEntry gains artist/album/track_no (reuses duration/thumb_hash/
  display_title, already generic). New musicbrainz_config/_enabled and
  music_meta_req/_resp message pairs, mirroring the TMDB shape.
- title_parse.parse_track_filename: track-number-prefix + title parsing,
  fallback-only (embedded tags are the primary source, unlike Videos).
- indexer.enrich_audio.AudioEnricher: mutagen-based tag/embedded-cover
  extraction through its own bounded pool (asyncio.to_thread, no
  subprocess — no ffmpeg-shaped deadlock risk). Gated on "music" in a
  group's enabled_apps rather than a video_root-style scoped folder.
- musicbrainz.py: MusicBrainzClient — no API key (unlike TMDB), just a
  self-imposed ~1 req/s pace and a configurable, non-default User-Agent
  contact string; inert (no calls at all) when no contact is configured,
  never sends an unidentified client.
- media_cache.py: file_mbid/mbid_meta tables alongside the existing TMDB
  ones, cover art reusing the thumbs table via a synthetic
  musicbrainz:{mbid} id, pruned on file deletion.
- roster.py/ops.py/webrtc_server.py: musicbrainz_contact (node-wide) and
  musicbrainz_enabled (per-group, from the start) as signed operator
  settings, ALLOWED_APPS gains "music", _do_music_meta_request resolves
  and caches a release-level MusicBrainz match per (artist, album).
- daemon.py: AudioEnricher/MusicBrainzClient wired alongside the video
  ones; a group's existing library is swept when "music" is newly
  enabled (no video_root equivalent — see musicbay.md §2.1).

41 new tests (musicbrainz.py against a mocked transport, admin-op policy
for both new settings, media_cache round-trip/pruning, enrich_audio
end-to-end against real ffmpeg-generated MP3s). Full suite (common +
node + hub): 1116 passed, no regressions.

Client-side (music-app.js, persistent player bar) not started yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KBi7ALLGfwcjBXt57yNMcy

1 files changed, 68 insertions, 9 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/media_cache.py b/packages/meshbay-node/src/meshbay_node/media_cache.py
index 6daae3f..47032b8 100644
--- a/packages/meshbay-node/src/meshbay_node/media_cache.py
+++ b/packages/meshbay-node/src/meshbay_node/media_cache.py
@@ -1,11 +1,17 @@
 """
-MeshBay Node — TMDB metadata and thumbnail cache for the Videos group app.
+MeshBay Node — TMDB/MusicBrainz metadata and thumbnail cache, shared by the
+Videos and Music group apps.
 
 Node-wide (not per-group, `data_dir/media_cache.db`), same rationale as
-`tmdb_enabled`/`tmdb_api_token` living in `group_settings` under the
-`group_id=""` sentinel (docs/mediacenter.md §5.5): TMDB is one operator's
-budget and credential, and a thumbnail is the same bytes regardless of which
-group happens to share the file.
+`tmdb_enabled`/`tmdb_api_token` (and `musicbrainz_enabled`/
+`musicbrainz_contact`, docs/musicbay.md §6) living in `group_settings` under
+the `group_id=""` sentinel (docs/mediacenter.md §5.5): the credential/budget
+is one operator's, and a thumbnail or cover image is the same bytes
+regardless of which group happens to share the file. The `file_mbid`/
+`mbid_meta` tables below are the Music app's equivalent of `file_tmdb`/
+`tmdb_meta`, sharing the same `thumbs` table for cover art (a MusicBrainz
+release's cover is cached under a synthetic `musicbrainz:{mbid}` file_id,
+the same trick `_fetch_and_cache_poster` uses for a TMDB poster_path).
 
 Disposable and rebuildable, like the rest of the file index (§1, §2) — never
 a second identity for a file. Every row here is keyed off a value the node
@@ -48,15 +54,28 @@ CREATE TABLE IF NOT EXISTS season_meta (
     fetched_at  REAL NOT NULL,
     PRIMARY KEY (tmdb_id, season)
 );
+CREATE TABLE IF NOT EXISTS file_mbid (
+    file_id     TEXT PRIMARY KEY,
+    mbid        TEXT NOT NULL
+);
+CREATE TABLE IF NOT EXISTS mbid_meta (
+    mbid        TEXT PRIMARY KEY,
+    json        TEXT NOT NULL,
+    fetched_at  REAL NOT NULL
+);
 """
 
 # TMDB overviews/ratings do drift; a file's own resolved tmdb_id does not
 # need re-checking on this schedule, only the metadata blob (§5.4, V3).
 TMDB_META_TTL_SECS = 30 * 86400
 
+# Same default as TMDB (docs/musicbay.md §6) — MusicBrainz release data is
+# not expected to drift faster; revisit if that proves wrong in practice.
+MUSICBRAINZ_META_TTL_SECS = 30 * 86400
+
 
 class MediaCache:
-    """Async SQLite cache for TMDB lookups and generated thumbnails."""
+    """Async SQLite cache for TMDB/MusicBrainz lookups and generated thumbnails/cover art."""
 
     def __init__(self, db_path: Path):
         self._db_path = db_path
@@ -144,6 +163,44 @@ class MediaCache:
         )
         await self._db.commit()
 
+    # ── file -> musicbrainz release id mapping (Music app) ───────────────────
+
+    async def get_file_mbid(self, file_id: str) -> str | None:
+        async with self._db.execute(
+            "SELECT mbid FROM file_mbid WHERE file_id = ?", (file_id,),
+        ) as cur:
+            row = await cur.fetchone()
+        return row[0] if row else None
+
+    async def set_file_mbid(self, file_id: str, mbid: str) -> None:
+        await self._db.execute(
+            "INSERT OR REPLACE INTO file_mbid (file_id, mbid) VALUES (?, ?)",
+            (file_id, mbid),
+        )
+        await self._db.commit()
+
+    # ── musicbrainz release id -> metadata json (Music app) ───────────────────
+
+    async def get_mbid_meta(self, mbid: str) -> dict | None:
+        """Returns None on a miss or on an entry older than MUSICBRAINZ_META_TTL_SECS."""
+        async with self._db.execute(
+            "SELECT json, fetched_at FROM mbid_meta WHERE mbid = ?", (mbid,),
+        ) as cur:
+            row = await cur.fetchone()
+        if not row:
+            return None
+        raw_json, fetched_at = row
+        if time.time() - fetched_at > MUSICBRAINZ_META_TTL_SECS:
+            return None
+        return json.loads(raw_json)
+
+    async def set_mbid_meta(self, mbid: str, meta: dict) -> None:
+        await self._db.execute(
+            "INSERT OR REPLACE INTO mbid_meta (mbid, json, fetched_at) VALUES (?, ?, ?)",
+            (mbid, json.dumps(meta), time.time()),
+        )
+        await self._db.commit()
+
     # ── thumbnails ────────────────────────────────────────────────────────────
 
     async def get_thumb(self, thumb_hash: str) -> bytes | None:
@@ -179,10 +236,12 @@ class MediaCache:
     async def prune_file(self, file_id: str) -> None:
         """
         Called when a file leaves the index (deletion, unshared root). Removes
-        its thumbnail and its file->tmdb mapping. `tmdb_meta` rows are left
-        alone — they're keyed by tmdb_id, not file_id, and other files (other
-        episodes of the same show) may still reference the same entry.
+        its thumbnail and its file->tmdb/file->mbid mappings. `tmdb_meta`/
+        `mbid_meta` rows are left alone — they're keyed by tmdb_id/mbid, not
+        file_id, and other files (other episodes of the same show, other
+        tracks of the same release) may still reference the same entry.
         """
         await self._db.execute("DELETE FROM thumbs WHERE file_id = ?", (file_id,))
         await self._db.execute("DELETE FROM file_tmdb WHERE file_id = ?", (file_id,))
+        await self._db.execute("DELETE FROM file_mbid WHERE file_id = ?", (file_id,))
         await self._db.commit()