feat(stream): serve /stream from a debrid HTTPS link (hueco #2/2a)

The daemon can now stream a session straight from a server-resolved debrid
direct URL instead of disk/torrent, delivering the "play instantáneo
cache-fast" promise for cache-confirmed torrents the user never downloaded.

- debridFileProvider: an io.ReadSeekCloser over HTTP Range — network-free
  Seek, lazy GET on Read, reopen-on-seek, a HEAD up front for the size, and
  a URL-derived name so the served Content-Type is video/mp4 (not
  octet-stream) when the web's name lacks an extension.
- OnStreamSession branches on StreamSession.DirectURL before the filePath
  checks (no local path, no ffmpeg), builds the provider in a goroutine
  (HEAD off the sync loop) and marks the session ready.
- Bump 0.10.0 -> 0.11.0 as the debrid-stream floor the web gates on.

Validated e2e against a real AllDebrid account: a cached mp4 plays 1080p in
Chrome through the agent, including the high-offset seek for a non-faststart
file's moov atom. 2b (HLS-from-URL for mkv/HEVC) + 2c (cache-fast preference
+ mid-stream fallback) remain.

internal/agent/types.go

@@ -417,6 +417,15 @@ type StreamSession struct {
 	//              the raw file over /stream (HTTP Range, no ffmpeg) instead of
 	//              transcoding to HLS. See hueco #3 phase 3a in the roadmap.
 	PlayMethod string `json:"playMethod,omitempty"`
+	// DirectURL, when set, is an HTTPS link to the media resolved server-side
+	// from the user's debrid account (hueco #2 / 2a). The source has no local
+	// file: the daemon streams /stream from this URL via ranged GETs
+	// (debridFileProvider) instead of from disk/torrent. Carries the "play
+	// instantáneo cache-fast" promise — the web only sets it when the hash is
+	// confirmed debrid-cached and the container is browser-native (mp4/m4v),
+	// and gates it on an agent-version floor so older daemons never receive a
+	// field they can't serve. Takes priority over FilePath when present.
+	DirectURL string `json:"directUrl,omitempty"`
 }
 
 // SyncResponse is returned by the server with all pending actions for the CLI.