Add Google Photos-style justified row layout as a mode within masonry:
- Add masonryMode setting: 'columns' (Pinterest) or 'rows' (Google Photos)
- Create justifiedLayoutCalculator utility for row-based layouts
- Extract and store image dimensions on upload for layout calculations
- Include width/height in gallery API response
- Add row height and last row behavior controls to theme customizer
- Support responsive container width detection with ResizeObserver
Photos in rows mode maintain their aspect ratios while filling
horizontal rows at a consistent height. The number of photos per
row is automatically calculated based on target row height and
photo dimensions.
Closes#146
Paul Nothaft
e081b56a44