muse: request a single song, get it tagged in your library

Lidarr's smallest unit is a MusicBrainz release, so asking for one track
means monitoring a whole discography. Soulseek trades individual files but
has no concept of a request. muse bridges the two: search, click, and the
song lands in the library correctly tagged.

The design point is that the user picks the exact track before anything
downloads, so muse holds artist, album, year and track number as ground
truth and tags deterministically rather than inferring them afterwards from
whatever a stranger named the file.

Search is Deezer rather than MusicBrainz, decided on measurement:
MusicBrainz put eight covers above the real recording for "radiohead creep"
and never surfaced Queen for "bohemian rhapsody" across 90 results, because
its index matches a word in a cover's title as readily as in the artist
field. Re-ranking cannot rescue a result set missing the right row.

Imports are os.link(), so downloads keep seeding from the Soulseek share
while the library gets a second name for the same bytes.

Dockerfile

@@ -0,0 +1,20 @@
+# Slim, no build toolchain needed — every dependency ships wheels for
+# linux/amd64 on py3.12.
+FROM python:3.12-slim
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY app.py .
+COPY static ./static
+
+# Runs as 1000:1000 via the compose `user:` key, matching every other
+# container that touches /data. Nothing here needs root.
+EXPOSE 5040
+
+HEALTHCHECK --interval=60s --timeout=10s --start-period=15s --retries=3 \
+  CMD python -c "import urllib.request,sys; sys.exit(0 if urllib.request.urlopen('http://127.0.0.1:5040/api/health',timeout=8).status==200 else 1)"
+
+CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "5040", "--no-access-log"]