fix(torrent): expand tracker list, add DHT persistence and configurable timeouts

- Expand default trackers from 5 to 31 (synced with web tracker-list.ts)
- Add DHT node persistence between sessions (~/.local/share/unarr/dht-nodes.txt)
  Saves known nodes on shutdown, restores on startup for warm DHT bootstrap
- Make metadata_timeout and stall_timeout configurable in config.toml
  Default: 0 (unlimited, like qBittorrent) — users can set custom values
- Fix CleanTitle to handle web domains and format patterns (e.g. pctfenix.com)

internal/library/resolve_test.go

@@ -143,6 +143,7 @@ func TestCleanTitle(t *testing.T) {
 		{"Breaking.Bad.S01E05.720p.HDTV.mkv", "Breaking Bad S01E05"},
 		{"The.Matrix.1999.2160p.UHD.BluRay.REMUX.mkv", "The Matrix"},
 		{"Movie [YTS.MX].mp4", "Movie"},
+		{"Greenland 4Kremux2160.pctfenix.com.mkv", "Greenland"},
 	}
 
 	for _, tt := range tests {