Add kiosk desktop app

Tauri app for the Pi. Media runs through the native LiveKit SDK because
WebKitGTK has no WebRTC, with frames encoded in Rust and drawn to a canvas
under the annotation overlay.

Claude-Session: https://claude.ai/code/session_01SS9F92jb51bMCRCKem6QtD

apps/kiosk-client/.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+  "recommendations": [
+    "svelte.svelte-vscode",
+    "tauri-apps.tauri-vscode",
+    "rust-lang.rust-analyzer"
+  ]
+}

apps/kiosk-client/.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "svelte.enable-ts-plugin": true
+}