fix: elevate CSS priority to override GTK4 user theme (v0.6.1)

Colloid-Catppuccin theme loaded via ~/.config/gtk-4.0/gtk.css at
PRIORITY_USER (800) was overriding moongreet's PRIORITY_APPLICATION (600),
causing avatar to lose its circular border-radius.

- Use STYLE_PROVIDER_PRIORITY_USER for app CSS provider
- Replace border-radius: 50% with 9999px (GTK4 CSS percentage quirk)
- Include missed Cargo.lock and PKGBUILD updates from v0.6.0

pkg/PKGBUILD

@@ -4,7 +4,7 @@
 # Maintainer: Dominik Kressler
 
 pkgname=moongreet-git
-pkgver=0.3.1.r5.g4c9b436
+pkgver=0.4.0.r7.g77b94a5
 pkgrel=1
 pkgdesc="A greetd greeter for Wayland with GTK4 and Layer Shell"
 arch=('x86_64')