feat(stream): transcode debrid sources to HLS from a URL (hueco #2/2b)

Non-browser-native debrid content (mkv/HEVC/…) can now stream: ffmpeg reads
the debrid HTTPS link directly (-i <url>) and transcodes to HLS, instead of
2a's raw direct-play which only works for mp4/m4v.

- HLSSessionConfig gains SourceURL + CacheID; sourceRef() feeds ffprobe,
  ffmpeg -i, and subtitle extraction from one place. HTTP-resilience flags
  (-reconnect*, -rw_timeout) are added only for a URL source; a seek-restart
  re-opens the URL with a Range request (-ss before -i = input seek).
- Segment cache keys by CacheID (the torrent info_hash) for URL sessions so
  re-plays hit cache despite the debrid URL changing each resolution
  (KeyForID, no filepath.Abs).
- OnStreamSession: the 2a direct-play branch is now gated on PlayMethod != "hls";
  a new branch handles DirectURL + PlayMethod=="hls" → HLS-from-URL. The
  local-file and both debrid HLS paths share a startHLSPlayback helper.
- ExtractMediaInfo no longer masks a URL probe failure as "file not found"
  (surfaces ffprobe's real stderr, e.g. "Protocol not found" on a TLS-less
  ffmpeg build).
- Bump 0.11.0 -> 0.12.0 as the HLS-from-URL floor the web gates on.

Validated e2e against real AllDebrid: a cached HEVC x265 mkv transcodes
(h264_nvenc) from the debrid URL and plays 1080p in Chrome via hls.js,
subtitles extracted from the remote mkv.

internal/cmd/version.go

@@ -1,4 +1,4 @@
 package cmd
 
 // Version is the CLI version. Overridden by goreleaser ldflags at release time.
-var Version = "0.11.0"
+var Version = "0.12.0"