[sergej-koscejev]

Summary

Adds .github/renovate.json5: config:best-practices, monthly schedule, updates grouped into a few PRs.

monthly
├── non-major dependencies   gradle + gradle-wrapper minor/patch
├── Gradle                   majors of wrapper + foojay-resolver
├── Kotlin                   majors of Kotlin plugin + kotlin-stdlib (one catalog version)
├── GitHub Actions           all updates, majors included
├── lock file maintenance    monthly instead of weekly from best-practices
└── other majors             one PR each

Lock file maintenance stays on: the Gradle lock files pin what dynamic versions (the launcher's 2.8.0.+) and
transitive dependencies resolve to. Because the publication uses resolved versions, it also changes the launcher build
that users get.

Evidence

renovate-config-validator --strict (renovate 44.179.0): Config validated successfully.

Local dry run (--platform=local --dry-run=full):

• Before (only config:best-practices + schedule:monthly): 18 branches, Kotlin plugin and kotlin-stdlib in
  separate branches that edit the same catalog line.

  After: 6 branches:

  Branch	Updates
  renovate/non-major-dependencies	launcher 2.8.0.+ → 2.9.2.+, Gradle 8.14.6, foojay 0.10.0, Kotlin 1.9.25, binary-compatibility-validator 0.18.2
  renovate/major-gradle	Gradle 9.8.2, foojay 1.0.0
  renovate/major-kotlin	Kotlin 2.4.21
  renovate/major-semver	semver 2.1.0
  renovate/github-actions	checkout, setup-java, upload-artifact, gradle/actions, action-junit-report
  renovate/lock-file-maintenance	lock files

Merge Danger

Blast Radius: none

Config only. Renovate PRs that follow can raise users' minimum Gradle or Kotlin version and change the published
launcher version; each needs review before merge.