Fix CRT shader: add program_opencl to required filters whitelist

SupportsFilter("program_opencl") always returned false because
program_opencl was missing from the _requiredFilters list in
EncoderValidator. GetFFmpegFilters() only reports filters that are
in that whitelist, so IsCrtShaderEnabled() was silently always false.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

MediaBrowser.MediaEncoding/Encoder/EncoderValidator.cs

@@ -125,6 +125,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
             "transpose_opencl",
             "yadif_opencl",
             "bwdif_opencl",
+            "program_opencl",
             // vaapi
             "scale_vaapi",
             "deinterlace_vaapi",