Fix release compliancy issues

Problems found

• Building from the 3.0.0 source ZIP fails without a .git directory (build number retrieval expects git).
• NOTICE files have outdated years; Groovy notice references legacy (Codehaus) text instead of Apache Groovy/ASF.

Acceptance criteria

• mvn clean install succeeds from the 3.0.0 source ZIP without requiring a git repository.

• Root NOTICE, NOTICE.template, and package NOTICE reflect 2015-2025 and use Apache Groovy/ASF wording.

• Assembled distribution includes LICENSE and NOTICE as required.

• RAT report shows 0 unknown licenses.