add renovatebot

[joshuafernandes]

Note

Low Risk
Mostly adds CI/configuration for dependency update PRs; main risk is misconfiguration or secret/env setup causing noisy PRs or failed workflow runs.

Overview
Introduces Renovatebot automation via a new GitHub Actions workflow (.github/workflows/renovatebot.yml) that runs on a monthly schedule (and on workflow changes) using repository secrets for a GitHub App.

Adds renovate.json to enable GitHub Actions and Gradle managers, pin action digests, and group updates with a 7-day minimum release age, and adds CODEOWNERS rules for overall ownership plus .github/workflows/ ownership.

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