refactor(branding): rename project to LockScreenWallpaper across repo

Standardize branding by renaming Wechselbild to LockScreenWallpaper.
This updates UI strings, configs, and plugin metadata for consistency.

- Rename branding across UI, docs, and config in the repo
- Update Android UI strings and notification titles to LockScreenWallpaper

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

@@ -29,7 +29,7 @@ class WallpaperRotationService : Service() {
     val pending = PendingIntent.getActivity(this, 0, launch, PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT)
     val notification = NotificationCompat.Builder(this, CHANNEL)
       .setSmallIcon(android.R.drawable.ic_menu_gallery)
-      .setContentTitle("Wechselbild ist aktiv")
+      .setContentTitle("LockScreenWallpaper ist aktiv")
       .setContentText("Das Motiv wechselt beim Aktivieren des Displays.")
       .setOngoing(true).setSilent(true).setContentIntent(pending).build()
     startForeground(NOTIFICATION_ID, notification)