fix: address audit findings — blur channel mismatch, logout quit, config error logging

- Fix BGRA→RGBA channel swap in apply_blur so image::RgbaImage semantics
  match the actual pixel data from GDK texture download
- Logout now calls app.quit() like lock does, via new quit_after field on
  ActionDef (replaces fragile magic string comparison)
- Log TOML parse errors to stderr instead of silently ignoring
- Remove pointless zlib compression of JPEG wallpaper in GResource
- Add tests for quit_after behavior and config error handling

resources/resources.gresource.xml

@@ -2,7 +2,7 @@
 <gresources>
   <gresource prefix="/dev/moonarch/moonset">
     <file>style.css</file>
-    <file compressed="true">wallpaper.jpg</file>
+    <file>wallpaper.jpg</file>
     <file>default-avatar.svg</file>
   </gresource>
 </gresources>