Server idle timeout 120s, and say why there is no read timeout

Family idea #5105, practice 9 (Scribe #5113). The body cap was already
there (MAX_CONTENT_LENGTH, 64 MiB). For timeouts, read from hypercorn
0.18's source:

- --keep-alive goes from 600 to 120. It is also the header timeout:
  hypercorn marks a connection busy only once a whole request has
  arrived, so a client dribbling headers was allowed ten minutes per
  connection. 120 stays above Traefik's 90s backend idle timeout, so the
  proxy never reuses a connection this server just closed.
- No --read-timeout, deliberately. It bounds every socket read, including
  the whole of a streaming download while the client sends nothing, so it
  would cut off an APK fetched slowly over mobile data.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile

@@ -57,4 +57,16 @@ EXPOSE 5000
 # Wait for the database, run migrations, then serve. The DB wait keeps a briefly
 # slow/unready database from crash-looping the container. Family convention
 # (rule 82): schema is built by real migrations, never metadata.create_all.
-CMD ["sh", "-c", "python -m inkwell.dbwait && alembic upgrade head && hypercorn 'inkwell.app:create_app()' --bind 0.0.0.0:5000 --keep-alive 600"]
+#
+# Timeouts (family idea #5105, practice 9; read from hypercorn 0.18's source):
+# - `--keep-alive 120` is the idle timeout. It is also the header timeout:
+#   hypercorn marks a connection busy only once a whole request has arrived, so a
+#   client dribbling headers is still "idle" and is cut off at this. It was 600,
+#   ten minutes per held connection. 120 stays above Traefik's 90s idle timeout
+#   for backend connections, so the proxy never reuses one this server has just
+#   closed (a 502).
+# - No `--read-timeout`, on purpose. It bounds every socket read, including the
+#   whole time a download is streaming and the client sends nothing, so it would
+#   cut off an APK fetched slowly over mobile data. Bodies are capped instead
+#   (MAX_CONTENT_LENGTH in app.py).
+CMD ["sh", "-c", "python -m inkwell.dbwait && alembic upgrade head && hypercorn 'inkwell.app:create_app()' --bind 0.0.0.0:5000 --keep-alive 120"]