Upgrade to IntelliJ Platform 2024.3

[gordolio]

Breaking Changes

• ⚠️ Requires Java 21+ (upgraded from Java 17)
• ⚠️ Requires IntelliJ IDEA 2024.3+ (upgraded from 2024.1)
• ⚠️ Plugin version: 2024.3.1

Dependencies Updated

• Kotlin: 1.9.25 → 2.2.21
• Gradle IntelliJ Platform Plugin: 1.17.4 (v1) → 2.10.1 (v2)
• IntelliJ Platform: 2024.1 → 2024.3.6
• Handlebars plugin: 241.14494.150 → 243.21565.122

Build Configuration

• Added pluginVerification.ides configuration (required by Gradle IntelliJ Platform Plugin v2)
• Updated JVM target from 17 → 21

CI/CD

• Updated GitHub Actions workflows (ci.yml, release.yml) to use Java 21

Compatibility

• ✅ Compatible with IntelliJ IDEA 2024.3, 2025.1, and 2025.2+
• ✅ Broader user base than targeting 2025.2 only