Improve error handling and disable buttons while processing
Adjust segmenter preview quality (0.5 -> 0.25)
Add built-in photo gallery (including 8 CC-BY or CC0 photos)
Allow navigating to effect page only if segmentation was successful
Revert "Adjust segmenter preview quality (0.5 -> 0.25)"

This reverts commit 8d875da80cbb79bd7240be52b51d638f05de7c87.
Add missing built-in gallery page files
Add more built-in gallery photos
Replace plain grid gallery with a static mosaic style layout
Move reset (clear all annotations) from button to menu
Fix: Pressing back while processing plays the transition animation
Update application help text
Adjust built-in gallery thumbnail bitmap size
Fix: Application crashes when returning from effect selection
Keep effect settings (shape and size) between effect selection events
Adjust segmentation and effect page layout
Change gallery "photos" label to "open from albums..."
Update blur kernel shape icons (they now match actual kernel shapes)
Add photo attributions link to about page
Update attributions text file