feat: select input devices for recordings

Closes #68

js/src/stores/media-devices-store.ts

@@ -0,0 +1,50 @@
+import { create } from "zustand";
+
+export interface SavedDevice {
+  deviceId: string;
+  label: string;
+}
+
+const MIC_KEY = "llink:mic-device";
+const CAMERA_KEY = "llink:camera-device";
+
+function load(key: string): SavedDevice | null {
+  try {
+    const raw = localStorage.getItem(key);
+    if (!raw) return null;
+    const parsed = JSON.parse(raw) as SavedDevice;
+    if (typeof parsed?.deviceId !== "string") return null;
+    return { deviceId: parsed.deviceId, label: parsed.label ?? "" };
+  } catch {
+    return null;
+  }
+}
+
+function save(key: string, value: SavedDevice | null) {
+  try {
+    if (value) localStorage.setItem(key, JSON.stringify(value));
+    else localStorage.removeItem(key);
+  } catch {
+    // Storage unavailable
+  }
+}
+
+interface MediaDevicesState {
+  mic: SavedDevice | null;
+  camera: SavedDevice | null;
+  setMic: (device: SavedDevice | null) => void;
+  setCamera: (device: SavedDevice | null) => void;
+}
+
+export const useMediaDevicesStore = create<MediaDevicesState>((set) => ({
+  mic: load(MIC_KEY),
+  camera: load(CAMERA_KEY),
+  setMic: (device) => {
+    save(MIC_KEY, device);
+    set({ mic: device });
+  },
+  setCamera: (device) => {
+    save(CAMERA_KEY, device);
+    set({ camera: device });
+  },
+}));