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/config/config.go

@@ -41,6 +41,9 @@ type DownloadConfig struct {
 	MaxConcurrent    int    `toml:"max_concurrent"`
 	MaxDownloadSpeed string `toml:"max_download_speed"` // e.g. "10MB", "500KB", "0" = unlimited
 	MaxUploadSpeed   string `toml:"max_upload_speed"`   // e.g. "1MB", "0" = unlimited
+	MetadataTimeout  string `toml:"metadata_timeout"`   // e.g. "1h", "30m", "0" = unlimited (default: "0")
+	StallTimeout     string `toml:"stall_timeout"`      // e.g. "30m", "1h", "0" = unlimited (default: "30m")
+	ListenPort       int    `toml:"listen_port"`        // fixed port for incoming peer connections (default: 42069, 0 = random)
 }
 
 type OrganizeConfig struct {