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

src/download.rs

@@ -258,20 +258,6 @@ pub fn matches_keywords(keywords: &[String], haystacks: &[&str]) -> bool {
     })
 }
 
-/// Formats a progress line, throttled by the caller to ~1% steps as the original's
-/// lastDLStepSize guard did.
-pub fn progress_line(name: &str, done: u64, total: Option<u64>) -> String {
-    match total {
-        Some(t) if t > 0 => format!(
-            "    {name}: {:.1}% ({:.1}/{:.1} MB)",
-            done as f64 / t as f64 * 100.0,
-            done as f64 / 1_048_576.0,
-            t as f64 / 1_048_576.0
-        ),
-        _ => format!("    {name}: {:.1} MB", done as f64 / 1_048_576.0),
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;