Migrate to IntelliJ Platform Gradle Plugin 2.x (#131)

- Gradle: 8.1.1 → 9.4.1
- IntelliJ Plugin: org.jetbrains.intellij 1.14.1 → org.jetbrains.intellij.platform 2.13.0
- Kotlin: 1.8.21 → 2.1.20
- Platform: 2024.2 → 2025.3.4
- Compatibility: up to 261.* (IntelliJ 2026.1)
- Kover: 0.7.1 → 0.9.1, Changelog: 2.1.0 → 2.2.1
- Removed Qodana plugin (API incompatible, was disabled in CI)
- Updated CI action versions (checkout v4, setup-java v4, etc.)

Bump (#130)

* Bump

* Bump

* Limit ide versions for verification!

* 2025.2, not 2025.3

* Bump platformVersion

* Change pluginVerifierIdeVersions to IU-2025.2 for IntelliJ Ultimate...

Bump (#128)

Version bump (#127)

Co-authored-by: Eirik Brandtzæg <[email protected]>

Bump upload-artifact to v4 (#123)

Update gradle.properties (#121)

Bump 242 (#119)

Bump. I hope (#118)

Bump (#116)

* Bump

Version bump (#113)

* Version bump