feat: implement settings engine with directory picker and aria2 configuration sync

src/hooks/useDirectoryPicker.ts

@@ -0,0 +1,22 @@
+import { open } from '@tauri-apps/plugin-dialog';
+
+export const useDirectoryPicker = () => {
+  const pickDirectory = async (defaultPath?: string): Promise<string | null> => {
+    try {
+      const selected = await open({
+        directory: true,
+        multiple: false,
+        defaultPath: defaultPath,
+      });
+      if (selected && typeof selected === 'string') {
+        return selected;
+      }
+      return null;
+    } catch (e) {
+      console.error('Failed to pick directory:', e);
+      return null;
+    }
+  };
+
+  return { pickDirectory };
+};