refactor: remove embedded wallpaper from binary (v0.6.2)

Wallpaper is installed by moonarch to /usr/share/moonarch/wallpaper.jpg.
Embedding a 374K JPEG in the binary was redundant. Without a wallpaper
file, GTK background color (Catppuccin Mocha base) shows through.

CLAUDE.md

@@ -19,7 +19,7 @@ Teil des Moonarch-Ökosystems.
 ## Projektstruktur
 
 - `src/` — Rust-Quellcode (main.rs, lockscreen.rs, auth.rs, fingerprint.rs, config.rs, i18n.rs, users.rs, power.rs)
-- `resources/` — GResource-Assets (style.css, wallpaper.jpg, default-avatar.svg)
+- `resources/` — GResource-Assets (style.css, default-avatar.svg)
 - `config/` — PAM-Konfiguration und Beispiel-Config
 
 ## Kommandos