Initial implementation of songbook toolset

Kotlin/JVM multi-module project for generating a scout songbook PDF
from ChordPro-format text files. Includes ChordPro parser, layout engine
with greedy spread packing for double-page songs, OpenPDF renderer,
CLI (Clikt), Compose Desktop GUI, and 5 sample songs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

buildSrc/build.gradle.kts

@@ -0,0 +1,12 @@
+plugins {
+    `kotlin-dsl`
+}
+
+repositories {
+    mavenCentral()
+    gradlePluginPortal()
+}
+
+dependencies {
+    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.10")
+}