chore(repo): add root Maven and Gradle files to Java reviewers in CODEOWNERS

[FrozenPandaz]

Current Behavior

Root Maven and Gradle build files (pom.xml, build.gradle.kts, settings.gradle.kts) are not explicitly assigned to the Java reviewers in CODEOWNERS.

Expected Behavior

With this PR, the Java reviewers (@FrozenPandaz @MaxKless @lourw) will be automatically added as reviewers when changes are made to:

• /pom.xml - Root Maven build file
• /build.gradle.kts - Root Gradle build file
• /settings.gradle.kts - Gradle settings file

This ensures the Java team has visibility into changes affecting the root Java build configuration.

Related Issue(s)

N/A - Maintenance improvement to CODEOWNERS