Add AMD AMF hardware acceleration option for MP4/MKV H.264 conversions

[bharatvansh]

This PR adds first-class AMD hardware acceleration support (AMF) to the FFmpeg conversion pipeline for H.264 video output.

What’s included

• Adds a new hardware acceleration mode: AMF (AMD Advanced Media Framework).
• Exposes AMF in Settings UI hardware acceleration dropdown.
• Maps AMF mode to localized display string (Advanced Media Framework (AMD)).
• Updates MP4/MKV conversion command generation to use AMF encoder:
  • -c:v h264_amf
  • -usage transcoding
  • -quality <speed|balanced|quality> (mapped from existing encoding speed setting)
  • -qp_i/-qp_p/-qp_b (mapped from existing quality slider)
• Keeps compatibility pixel format handling for non-CUDA paths by enforcing format=yuv420p where applicable.

Files changed

• Application/FileConverter/Helpers.cs
• Application/FileConverter/ViewModels/SettingsViewModel.cs
• Application/FileConverter/ValueConverters/HardwareAccelerationModeToString.cs
• Application/FileConverter/ConversionJobs/ConversionJob_FFMPEG.cs
• Application/FileConverter/ConversionJobs/ConversionJob_FFMPEG.Converters.cs

Validation performed

• Built and ran updated app binary.
• Confirmed Settings UI shows AMD hardware acceleration mode.
• Ran MP4 conversion with AMF selected and verified ffmpeg log contains:
  • stream mapping to h264_amf
  • successful conversion completion.

Notes

• This change targets AMD H.264 acceleration (AMF) for existing MP4/MKV workflow.
• No behavior change for Off and CUDA modes beyond shared command-generation refactor.

[bharatvansh]

Screenshots: