Add What's New dialog accessible from hamburger menu showing version
changelog. Add accessible property labels to step indicator for screen
reader support with current step/total announcements. Add focus
management on step transitions - focus moves to first interactive
element when navigating to a new step.
- Window size/position remembered between sessions via SessionStore
- Step indicator dots now clickable to navigate directly to that step,
with keyboard shortcut hints in tooltips
- File list in add-files dialog shows format and size per image,
header shows total count and total size
- Welcome dialog now saves skill level choice to config
- SessionState extended with window_width, window_height, window_maximized
7-step wizard flow (Workflow, Images, Resize, Convert, Compress,
Metadata, Output) with AdwNavigationView, step indicator dots,
Back/Next buttons, keyboard shortcuts (Alt+arrows, Alt+1-9),
and hamburger menu with Settings and History placeholders.
