Add a log view, and Docker packaging

The Log button shows the running daemon live: feed scans, downloads,
torrents and every HTTP request. It reads a ring buffer filled by a
tracing layer rather than tailing a file, so it works under Docker where
logs go to stdout. The access-log middleware skips /api/logs, or the
panel's poll would log itself forever.

Detached torrents could leave a row stuck in 'downloading' across a
restart, where nothing would ever revisit it; those are requeued at
startup.

Dockerfile, entrypoint and compose: 114 MB runtime, config bound to
0.0.0.0 on first run since container loopback is unreachable, drops to
PUID:PGID for Unraid, and a healthcheck that goes through the control
socket so a wedged worker reads as unhealthy.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AdXho5tTkjFLeUXKbEjKBh

.dockerignore

@@ -0,0 +1,4 @@
+target/
+.git/
+*.md
+tests/