fix: resolve emulator crash - thread safety and icon fallback

- NativeSearch: move onResult/onError callbacks outside withContext(Dispatchers.IO) to prevent CalledFromWrongThreadException
- SearchStrategy: change callback types to suspend to enable proper coroutine chaining
- SearchCoordinator: remove leaked CoroutineScope, rely on suspend callback chaining for fallback flow
- Resources: add mipmap-hdpi/mdpi/xhdpi/xxhdpi icon fallbacks for API < 26 devices

app/src/main/res/layout/item_search_result.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:padding="8dp"
+    android:background="@drawable/card_bg"
+    android:focusable="true"
+    android:clickable="true"
+    android:focusableInTouchMode="true">
+
+    <ImageView
+        android:id="@+id/iv_cover"
+        android:layout_width="200dp"
+        android:layout_height="120dp"
+        android:scaleType="centerCrop"
+        android:background="@color/surface" />
+
+    <TextView
+        android:id="@+id/tv_title"
+        android:layout_width="200dp"
+        android:layout_height="wrap_content"
+        android:ellipsize="end"
+        android:maxLines="1"
+        android:padding="4dp"
+        android:textColor="@color/text_primary"
+        android:textSize="14sp" />
+
+    <TextView
+        android:id="@+id/tv_category"
+        android:layout_width="200dp"
+        android:layout_height="wrap_content"
+        android:ellipsize="end"
+        android:maxLines="1"
+        android:padding="4dp"
+        android:textColor="@color/text_secondary"
+        android:textSize="12sp" />
+
+</LinearLayout>