chore: bump version to 0.4.0, add Gradle 9.6 wrapper, and finalize builds for NSIS, Docker, Fabric, Forge, and Paper

integrations/fabric/build.gradle

@@ -1,6 +1,6 @@
 plugins { id 'fabric-loom' version '1.8.13' }
-def mc = providers.gradleProperty('mcVersion').getOrElse('1.21.1')
-if (!(mc in ['1.20.1', '1.21.1'])) throw new GradleException('Use the modern build for 26.x')
+def mc = (providers.gradleProperty('mcVersion').orNull ?: project.findProperty('mcVersion') ?: '1.21.1').toString().trim()
+if (!['1.20.1', '1.21.1'].contains(mc)) throw new GradleException("Use the modern build for 26.x (got '${mc}')")
 def targetJava = mc == '1.20.1' ? 17 : 21
 loom { mixin { defaultRefmapName = 'scopenet.refmap.json' } }
 if (providers.gradleProperty('verifyMixins').isPresent()) {