feat: add gallery service and ML depth estimation placeholder

Media library access via new expo-media-library Query API,
image resize for wallpaper export, and MiDaS depth map
service stub for V1.5.

src/services/media/gallery.service.ts

@@ -0,0 +1,50 @@
+import * as MediaLibrary from "expo-media-library";
+import * as ImageManipulator from "expo-image-manipulator";
+import { Dimensions } from "react-native";
+
+const { width: SCREEN_WIDTH, height: SCREEN_HEIGHT } = Dimensions.get("screen");
+
+export async function requestGalleryPermission(): Promise<boolean> {
+  const { status } = await MediaLibrary.requestPermissionsAsync();
+  return status === "granted";
+}
+
+export async function getRecentPhotos(
+  count: number = 50,
+  offset: number = 0
+): Promise<{ assets: MediaLibrary.Asset[]; hasMore: boolean }> {
+  const query = new MediaLibrary.Query()
+    .eq(MediaLibrary.AssetField.MEDIA_TYPE, MediaLibrary.MediaType.IMAGE)
+    .orderBy({
+      key: MediaLibrary.AssetField.CREATION_TIME,
+      ascending: false,
+    })
+    .limit(count)
+    .offset(offset);
+
+  const assets = await query.exe();
+
+  return {
+    assets,
+    hasMore: assets.length === count,
+  };
+}
+
+export async function prepareImageForWallpaper(
+  uri: string
+): Promise<string> {
+  const result = await ImageManipulator.manipulateAsync(
+    uri,
+    [
+      {
+        resize: {
+          width: SCREEN_WIDTH * 2,
+          height: SCREEN_HEIGHT * 2,
+        },
+      },
+    ],
+    { compress: 0.95, format: ImageManipulator.SaveFormat.JPEG }
+  );
+
+  return result.uri;
+}