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.

src/main.rs

@@ -40,16 +40,16 @@ fn activate(app: &gtk::Application) {
     load_css(&display);
 
     let config = config::load_config(None);
-    let bg_path = config::resolve_background_path(&config);
-    let bg_texture = lockscreen::load_background_texture(&bg_path);
+    let bg_texture = config::resolve_background_path(&config)
+        .and_then(|path| lockscreen::load_background_texture(&path));
 
     if gtk4_session_lock::is_supported() {
-        activate_with_session_lock(app, &display, &bg_texture, &config);
+        activate_with_session_lock(app, &display, bg_texture.as_ref(), &config);
     } else {
         #[cfg(debug_assertions)]
         {
             log::warn!("ext-session-lock-v1 not supported — running in development mode");
-            activate_without_lock(app, &bg_texture, &config);
+            activate_without_lock(app, bg_texture.as_ref(), &config);
         }
         #[cfg(not(debug_assertions))]
         {
@@ -62,7 +62,7 @@ fn activate(app: &gtk::Application) {
 fn activate_with_session_lock(
     app: &gtk::Application,
     display: &gdk::Display,
-    bg_texture: &gdk::Texture,
+    bg_texture: Option<&gdk::Texture>,
     config: &config::Config,
 ) {
     let lock = gtk4_session_lock::Instance::new();
@@ -158,7 +158,7 @@ fn init_fingerprint_async(all_handles: Vec<lockscreen::LockscreenHandles>) {
 #[cfg(debug_assertions)]
 fn activate_without_lock(
     app: &gtk::Application,
-    bg_texture: &gdk::Texture,
+    bg_texture: Option<&gdk::Texture>,
     config: &config::Config,
 ) {
     let app_clone = app.clone();