feat(kiosk): live Kiosk<->Desktop toggle in the NPB layout menu

Add a "Kiosk mode" / "Desktop mode" item to both PlayerBarSmall and
PlayerBar view menus (label from the new ShellState.kiosk-profile flag).
It fires media-action("npb-view","","toggle-profile"); Rust flips the
persisted ui_prefs.profile and swaps the shell in place via set_screen
(KioskShell/AppShell share state, so no restart). The toggle keys off the
current screen, not kiosk_profile_active(), so a QBZ_PROFILE env override
doesnt pin it. ShellState.kiosk-profile is seeded at window setup.

cc

crates/qbz-ui/ui/state.slint

@@ -3724,6 +3724,9 @@ export global UiScale {
 // Globals are imported directly by the shell components, so toggles
 // need no callback plumbing.
 export global ShellState {
+    // Kiosk profile active (2.0.2 frente #3). Seeded from Rust at startup and
+    // flipped by the NPB "Kiosk/Desktop mode" toggle; drives that toggle's label.
+    in-out property <bool> kiosk-profile: false;
     // --- Reduce motion (weak renderer tiers) -------------------------------
     // Seeded from Rust: true on the femtovg-GL / software tiers, where every
     // animation frame is a full-window repaint on a weak GPU. When set,