- Eliminated layout_templates as separate entity — regions/grid now
live directly on layouts
- Displays created from kiosk pairing (not standalone), each display
has kiosk_id FK
- Removed Templates from sidebar nav and all template routes/pages
- Layout creation uses preset buttons (fullscreen, 2x2, 1+3, 3x3)
that set regions directly on the layout
- Setup no longer creates default display/layout (deferred to pairing)
- Pairing creates HDMI-0 display for new kiosk
- Bundle reads regions from layout directly, no template lookup
- Rust kiosk updated to match new bundle format
- DB migration adds regions/grid_cols/grid_rows to layouts, kiosk_id
to displays, copies existing template data
