style(expo): polish promo demo visual language

[AmatoGiulio]

Polishes the Expo promo demo without changing library/runtime behavior.

• keep Android status-bar content visible and follow system appearance
• use Expo Router Color.android.dynamic.* roles so RN surfaces follow the phone's Material You wallpaper/theme
• keep the promo flow on userInterfaceStyle: automatic
• mirror the supplied Google Photos Collections reference: Albums / Documents / Places / Moments grid, Screenshots / Videos / Recently Added / Sonu's photos / Archive / Locked list, compact backed-up header
• keep the React Native ScrollView as the only scroll owner
• mirror the floating Google Photos navigation labels: Photos / Spatial / Collections / Create
• show an icon only on the selected Collections tab; unselected tabs are text-only
• use a separate circular Search FAB
• keep the native Material FloatingToolbar on dynamic color and neutralize the Search FAB to a surface-container role

Validation note: demo-only changes. The two new Android drawable resources require prebuild/rebuild so they are copied into the native project. Dynamic color requires Android 12+ for wallpaper-derived Material You colors.