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/lockscreen.rs

@@ -44,7 +44,7 @@ struct LockscreenState {
 /// The `blur_cache` and `avatar_cache` are shared across monitors for multi-monitor
 /// setups, avoiding redundant GPU renders and SVG rasterizations.
 pub fn create_lockscreen_window(
-    bg_texture: &gdk::Texture,
+    bg_texture: Option<&gdk::Texture>,
     config: &Config,
     app: &gtk::Application,
     unlock_callback: Rc<dyn Fn()>,
@@ -86,9 +86,11 @@ pub fn create_lockscreen_window(
     let overlay = gtk::Overlay::new();
     window.set_child(Some(&overlay));
 
-    // Background wallpaper
-    let background = create_background_picture(bg_texture, config.background_blur, blur_cache);
-    overlay.set_child(Some(&background));
+    // Background wallpaper (if available — otherwise GTK background color shows through)
+    if let Some(texture) = bg_texture {
+        let background = create_background_picture(texture, config.background_blur, blur_cache);
+        overlay.set_child(Some(&background));
+    }
 
     // Centered vertical box
     let main_box = gtk::Box::new(gtk::Orientation::Vertical, 0);
@@ -430,18 +432,16 @@ pub fn start_fingerprint(
 }
 
 /// Load the wallpaper as a texture once, for sharing across all windows.
+/// Returns None if no wallpaper path is provided or the file cannot be loaded.
 /// Blur is applied at render time via GPU (GskBlurNode), not here.
-pub fn load_background_texture(bg_path: &Path) -> gdk::Texture {
-    let fallback = "/dev/moonarch/moonlock/wallpaper.jpg";
-
-    if bg_path.starts_with("/dev/moonarch/moonlock") {
-        let resource_path = bg_path.to_str().unwrap_or(fallback);
-        gdk::Texture::from_resource(resource_path)
-    } else {
-        let file = gio::File::for_path(bg_path);
-        gdk::Texture::from_file(&file).unwrap_or_else(|_| {
-            gdk::Texture::from_resource(fallback)
-        })
+pub fn load_background_texture(bg_path: &Path) -> Option<gdk::Texture> {
+    let file = gio::File::for_path(bg_path);
+    match gdk::Texture::from_file(&file) {
+        Ok(texture) => Some(texture),
+        Err(e) => {
+            log::warn!("Failed to load wallpaper {}: {e}", bg_path.display());
+            None
+        }
     }
 }