feat(wallpapers): add image crop support and i18n strings

Adds per-image image-crop support with persistent settings.
Rendering adapts to crop mode, zoom and position per image.
Locales the UI strings and notifications; app name updated.

- Cropping workflow with per-image crop state and rendering
- Localizes strings and notifications for en and de
- Introduces set_image_crop command and its permission schema

src-tauri/gen/android/app/src/main/res/values-de/strings.xml

@@ -0,0 +1,4 @@
+<resources>
+    <string name="app_name">WallpaperFlow</string>
+    <string name="main_activity_title">WallpaperFlow</string>
+</resources>

src-tauri/gen/android/app/src/main/res/values/strings.xml

@@ -1,4 +1,4 @@
 <resources>
-    <string name="app_name">"LockScreenWallpaper"</string>
-    <string name="main_activity_title">"LockScreenWallpaper"</string>
+    <string name="app_name">"WallpaperFlow"</string>
+    <string name="main_activity_title">"WallpaperFlow"</string>
 </resources>