Steps 7 and 8: torrents, OPML, and polish

librqbit replaces the vendored BitTorrent 4.2.1 tree. Torrents download
in place because seeding serves the files it downloaded, so the planned
stage-then-move would have broken it. The stall budget now also covers
magnet metadata resolution, which otherwise never returns against a dead
swarm and wedged the scan.

Adds add/rm/import/export, tracing setup, systemd units and README.

A successful swarm download is unverified: no reachable peers here.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RPyeapneuXrCdojsaiXGbe

contrib/ipx.timer

@@ -0,0 +1,16 @@
+# Alternative to the daemon: a periodic one-shot scan, closer to how the original
+# iPodderX agent was driven. Use this OR ipx.service, not both -- with no daemon
+# running there is no socket, so a UI cannot attach.
+#
+# Install ipx-scan.service and ipx.timer to ~/.config/systemd/user/, then
+#   systemctl --user enable --now ipx.timer
+[Unit]
+Description=Periodic ipx feed scan
+
+[Timer]
+OnBootSec=5min
+OnUnitActiveSec=1h
+Persistent=true
+
+[Install]
+WantedBy=timers.target