Fix recordings dying mid-stream; record to growing .ts with live buffer playback

A recording of a live event crashed partway through: when its short
Akamai token expired, the proxy's stale-alias check swapped the
recording's mapping to the most recently registered deferred stream,
of any content. Segment requests were then built against the wrong CDN
path, returned 403, and ffmpeg exited, splitting the recording into
several files.

Proxy:
- Never swap URN-backed livestreams; they refresh themselves from the
  API. Only consider swap candidates with the same URN.

Recording lifecycle:
- Complete a recording once its stream has been gone from the API for
  5 minutes (broadcasts can end before ValidTo).
- Fail a recording still waiting for its stream after ValidTo (or 12h
  after ValidFrom) instead of retrying forever.
- Wait for a DVR window whose start= is still in the future instead of
  starting ffmpeg against a 400/404.
- Keep the original start time across restarts; don't mark a recording
  failed on shutdown cancellation.

Growing .ts recordings:
- ffmpeg writes MPEG-TS (-c copy -copyts) to stdout and the plugin
  appends it to one file per recording, so restarts continue the same
  file and timeline.
- The Recordings folder lists any recording with a file on disk, not
  only completed ones.
- In-progress recordings are exposed as infinite streams reading through
  a new endpoint that follows the growing file (same pattern as
  Jellyfin's DVR), so they can be watched from the start like a
  livestream buffer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Jellyfin.Plugin.SRFPlay/Services/StreamProxyService.cs

@@ -132,10 +132,13 @@ public class StreamProxyService : IStreamProxyService
                 !string.IsNullOrEmpty(streamInfo.AuthenticatedUrl));
 
             // Check for stale alias: only look for fresher stream if current token is EXPIRED or EXPIRING SOON
-            // Don't replace a valid token (>5s left) with a new deferred registration
-            if (!streamInfo.NeedsAuthentication && tokenTimeLeft < 5)
+            // Don't replace a valid token (>5s left) with a new deferred registration.
+            // Livestreams with a URN refresh themselves from the API, so never swap them: an unrelated
+            // registration (e.g. from a library refresh) would point the stream at the wrong CDN path.
+            var selfRefreshing = streamInfo.IsLiveStream && !string.IsNullOrEmpty(streamInfo.Urn);
+            if (!streamInfo.NeedsAuthentication && tokenTimeLeft < 5 && !selfRefreshing)
             {
-                var freshStream = FindFreshestStream();
+                var freshStream = FindFreshestStream(streamInfo.Urn);
                 if (freshStream != null && freshStream.Value.Value.NeedsAuthentication)
                 {
                     _logger.LogWarning(
@@ -595,8 +598,9 @@ public class StreamProxyService : IStreamProxyService
     /// <summary>
     /// Finds the freshest (most recently registered) stream that needs authentication or has a valid token.
     /// </summary>
+    /// <param name="urn">When set, only streams for this URN are considered.</param>
     /// <returns>The freshest stream entry, or null if none found.</returns>
-    private KeyValuePair<string, StreamInfo>? FindFreshestStream()
+    private KeyValuePair<string, StreamInfo>? FindFreshestStream(string? urn)
     {
         var now = DateTime.UtcNow;
 
@@ -604,6 +608,11 @@ public class StreamProxyService : IStreamProxyService
         // or have tokens that aren't expired yet
         var candidates = _streamMappings.Where(kvp =>
         {
+            if (!string.IsNullOrEmpty(urn) && !string.Equals(kvp.Value.Urn, urn, StringComparison.OrdinalIgnoreCase))
+            {
+                return false; // Different content
+            }
+
             if (kvp.Value.NeedsAuthentication)
             {
                 return true; // Fresh deferred registration