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/main.rs

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