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/tauri.conf.json

@@ -1,9 +1,9 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
-  "productName": "LockScreenWallpaper",
+  "productName": "WallpaperFlow",
   "version": "0.1.0",
   "identifier": "de.wechselbild.app",
   "build": { "beforeDevCommand": "npm run dev", "devUrl": "http://localhost:1420", "beforeBuildCommand": "npm run build", "frontendDist": "../dist" },
-  "app": { "windows": [{ "title": "LockScreenWallpaper", "width": 420, "height": 860, "resizable": true }], "security": { "csp": null } },
-  "bundle": { "active": true, "targets": "all", "icon": [] }
+  "app": { "windows": [{ "title": "WallpaperFlow", "width": 420, "height": 860, "resizable": true }], "security": { "csp": null } },
+  "bundle": { "active": true, "targets": "all", "icon": ["icons/32x32.png", "icons/128x128.png", "icons/128x128@2x.png", "icons/icon.icns", "icons/icon.ico", "icons/icon.png"] }
 }