✨(frontend) add global store for browser permissions monitoring

Introduce new global state management to watch and expose browser
permissions status across the application.

Sets foundation for upcoming changes that will prevent the app from
offering hardware features (camera/microphone) when permissions are
not granted, improving user experience and reducing confusion.

src/frontend/src/stores/permissions.ts

@@ -0,0 +1,18 @@
+import { proxy } from 'valtio'
+
+type PermissionState =
+  | undefined
+  | 'granted'
+  | 'prompt'
+  | 'denied'
+  | 'unavailable'
+
+type State = {
+  cameraPermission: PermissionState
+  microphonePermission: PermissionState
+}
+
+export const permissionsStore = proxy<State>({
+  cameraPermission: undefined,
+  microphonePermission: undefined,
+})