Scaffold Java 21 multi-module project with UMD ISO + SFO parsing

- Gradle Kotlin DSL multi-module (core, ui, cli) with JPMS modules
- UMD ISO 9660 reader (UmdIsoReader/UmdIsoFile + sector devices)
- SFO (param.sfo) parser
- 'dump' CLI command: metadata + recursive file listing
- JUnit 5 + AssertJ tests (SFO and ISO reader)
- Switch license from MIT to GPL-3.0-or-later

cli/build.gradle.kts

@@ -0,0 +1,18 @@
+plugins {
+    application
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(21)
+    }
+}
+
+application {
+    mainModule = "dev.quoije.umd.cli"
+    mainClass = "dev.quoije.umd.cli.Main"
+}
+
+dependencies {
+    implementation(project(":core"))
+}