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

src-tauri/src/lib.rs

@@ -3,5 +3,5 @@ pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_wallpaper::init())
         .run(tauri::generate_context!())
-        .expect("error while running Wechselbild");
+        .expect("error while running LockScreenWallpaper");
 }

src-tauri/src/main.rs

@@ -1 +1 @@
-fn main() { wechselbild_lib::run(); }
+fn main() { lockscreenwallpaper_lib::run(); }