[perNyfelt]

Summary

Updates all outdated dependencies listed in #127:

Dependency	Old	New
Groovy (core, json, sql, swing)	5.0.7	6.0.0
Apache POI (poi-ooxml)	5.5.1	6.0.0
H2	2.4.240	2.5.252
FlatLaf	3.7.2	3.8
JUnit Jupiter / Platform	6.1.2	6.1.3
Spotless plugin	8.9.0	8.11.0
Ben-Manes versions plugin	0.57.0	0.67.0
Gradle wrapper	9.6.1	9.9.0

Changes beyond version bumps

• POI 6 API cleanup: CellStyle.getFontIndexAsInt() was removed in POI 6 (getFontIndex() already returned int since 5.5.1, so the *AsInt variant was redundant). Dropped the 7 usages of getFontIndexAsInt() in ReportServicesTest.groovy in favor of getFontIndex().
• Spotless 8.11.0 formatter: the updated greclipse formatter reformats continuation indentation in app/build.gradle (applied via ./gradlew spotlessApply; formatting-only, no functional change).
• Gradle wrapper fully regenerated: gradlew.bat and gradle-wrapper.jar updated to the 9.9.0 versions (jar checksum verified against gradle-9.9.0-wrapper.jar.sha256), and distributionSha256Sum added to gradle-wrapper.properties so the downloaded distribution is verified from now on.

Database impact

• H2 2.4 → 2.5: engine upgrade only — no schema or migration changes in this PR. H2 2.5 opens existing 2.4 database files transparently, so existing installations and backups keep working without any migration step.
• CodeNarc 4.0.0 still parses sources with Groovy 5 (no Groovy 6 CodeNarc release exists yet). This is fine today; if the codebase starts using Groovy 6-only syntax, codenarcMain/codenarcTest would fail to parse until a Groovy 6 CodeNarc variant is available.

Verification

• ./gradlew build passes in full: compilation (main + test), all unit/integration/acceptance tests, Spotless, and CodeNarc.
• Wrapper JAR SHA-256 verified against the official checksum published on services.gradle.org.