IMG-015: Incomplete JPEG Dimension Extraction

[murdore]

Summary

getImageDimensions() returns null for JPEGs instead of parsing SOF markers.

Root Cause

Lines 323-327 don't parse SOF0 (0xFFC0) or SOF2 (0xFFC2) markers.

Fix

Parse SOF markers to extract width/height from JPEG files.

Acceptance Criteria

• [ ] Implement SOF marker parsing
• [ ] Search for 0xFFC0 and 0xFFC2 markers
• [ ] Extract width and height from SOF marker data
• [ ] Handle edge cases (no SOF marker, truncated file)