Real backends + fetch/display workflows; config paths

Wire the incremental pipeline to real sources and expose two workflows.

Config (Env.py): three explicit paths — LOCAL_LIBRARY_PATH (scan source),
ITUNES_XML_PATH (manual export), DATA_DIR (storage root: DB + Spotify cache).

Real, incremental ingesters:
- local_scan: walks the library, skips files whose mtime/size are unchanged,
  prunes deleted ones, and reads embedded ISRC + recording MBID from tags
  (tagged files get real IDs with no network), via tags.py.
- itunes_xml: parse the iTunes Library.xml as a plist; skip if mtime unchanged.
- spotify_raw: ingest raw Spotify JSON (ISRC from external_ids); live fetch
  wrapper for when credentials are set.

Workflows (src/workflows.py + main.py):
- `fetch`  — pull + scan + parse + enrich + match, with readable step logs.
  First run is slow (full scan + MB lookups); later runs only touch changes
  (verified: ~71s first, ~0.6s second).
- `display` — launch the GUI.

Also: enrich uses ISRC-first again (local MBIDs now come from tags), fix
--enrich-limit 0, quiet musicbrainzngs XML warnings, ignore /data/.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Gui.py

@@ -45,7 +45,7 @@ def main():
         c1, c2, c3, c4, c5 = st.columns(5)
         c1.metric("Total", s["total"])
         c2.metric("Missing locally", s["missing"])
-        c3.metric("Have (MBID)", s["present_mbid"])
+        c3.metric("Have (ID)", s["present_mbid"])
         c4.metric("Have (text)", s["present_text"])
         coverage = (s["has_mbid"] / s["total"] * 100) if s["total"] else 0
         c5.metric("MBID coverage", f"{coverage:.0f}%")
@@ -54,8 +54,8 @@ def main():
     st.caption(
         f"Local library: {local.get('total', 0)} tracks, "
         f"{local.get('has_mbid', 0)} with a resolved MBID. "
-        "‘Have (MBID)’ = certain ID match; ‘Have (text)’ = normalized "
-        "artist/title match (run `enrich` to upgrade text matches to ID)."
+        "‘Have (ID)’ = certain ISRC/MBID match; ‘Have (text)’ = normalized "
+        "artist/title match (run `fetch`/`enrich` to upgrade text matches to ID)."
     )
 
     st.divider()