feat(wallpaper): extend commands with gallery, delete image, and crop

The plugin now exposes gallery retrieval, image deletion and image crop
across Android, desktop and mobile. The Rust core and Android
bridge are wired to handle these commands, updating state as needed.

- Add gallery, delete_image, and set_image_crop commands
- across Android, desktop and mobile.
- Update permissions, defaults, and schema to enable new commands.

plugins/android/src/main/java/WallpaperStore.kt

@@ -44,6 +44,45 @@ object WallpaperStore {
     }
   }
 
+  fun gallery(context: Context, offset: Int, limit: Int): JSObject {
+    val originals = files(context)
+    val selectedIndex = prefs(context).getInt(KEY_INDEX, 0).coerceIn(0, (originals.size - 1).coerceAtLeast(0))
+    val safeOffset = offset.coerceAtLeast(0).coerceAtMost(originals.size)
+    val safeLimit = limit.coerceIn(1, 100)
+    val items = JSArray()
+    originals.drop(safeOffset).take(safeLimit).forEachIndexed { pageIndex, file ->
+      items.put(JSObject().apply {
+        put("id", file.name)
+        put("url", thumbnailDataUrl(file))
+        put("selected", safeOffset + pageIndex == selectedIndex)
+      })
+    }
+    return JSObject().apply {
+      put("total", originals.size)
+      put("items", items)
+    }
+  }
+
+  @Synchronized
+  fun delete(context: Context, id: String): Boolean {
+    if (id.isBlank() || File(id).name != id) return false
+    val originals = files(context)
+    val position = originals.indexOfFirst { it.name == id }
+    if (position < 0 || !originals[position].delete()) return false
+
+    val preferences = prefs(context)
+    val previousIndex = preferences.getInt(KEY_INDEX, 0).coerceIn(0, (originals.size - 1).coerceAtLeast(0))
+    val remaining = originals.size - 1
+    val nextIndex = when {
+      remaining <= 0 -> 0
+      position < previousIndex -> previousIndex - 1
+      previousIndex >= remaining -> remaining - 1
+      else -> previousIndex
+    }
+    preferences.edit().putInt(KEY_INDEX, nextIndex).apply()
+    return true
+  }
+
   private fun thumbnailDataUrl(file: File): String {
     val bounds = BitmapFactory.Options().apply { inJustDecodeBounds = true }
     BitmapFactory.decodeFile(file.absolutePath, bounds)