HDR/HLG support and iPhone rotation handling

The transcoder picked up a series of fixes that close long-standing gaps with mobile and HDR source files. Rotation metadata embedded in iPhone side-data lists is now read and applied through software transpose, including for HDR/HLG inputs where hardware transpose was unsafe. Deprecated and unsupported pixel formats are auto-corrected before encoding, and rotation angles are validated so 90/180/270 rotations no longer produce stretched or letterboxed renditions. Together these changes make iPhone uploads, HDR clips, and odd-resolution sources transcode cleanly without manual reprocessing.