License Effector under the GPL, version 3 or later

LICENSE holds the text, the README and About Effector state it, and the
Arch package declares it. The version moves to 0.5.2 for the release.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packaging/arch/PKGBUILD

@@ -2,12 +2,12 @@
 # so pkgver must follow the project() line of CMakeLists.txt (the version core
 # test checks it). From this folder: makepkg -si
 pkgname=effector
-pkgver=0.5.1
+pkgver=0.5.2
 pkgrel=1
 pkgdesc='Image effects app: a GTK4 interface and a headless CLI over pluggable effects'
 arch=('x86_64' 'aarch64')
 url='https://git.plan9.uber.space/hans/effector'
-license=('unknown')
+license=('GPL-3.0-or-later')
 depends=('gtkmm-4.0' 'gdk-pixbuf2' 'pango' 'cairo' 'glib2' 'glibc' 'gcc-libs')
 makedepends=('cmake' 'ninja' 'git')
 checkdepends=('xorg-server-xvfb')