chore: update Renovate and Dependabot config

[olivermeyer]

Unifying our usage of Renovate vs Dependabot with other projects:

• Use Renovate exclusively for regular dependency updates and lock file management
  • Group all updates to GitHub Actions
  • Group all minor and patch updates to Python dependencies
• Use Dependabot only for security alerts and updates

The dependabot.yml file was referenced in a spec; I'm removing that line.

[Copilot]

Pull request overview

This PR consolidates dependency update tooling by making Renovate the sole tool for regular dependency version updates and lock file maintenance, while retaining Dependabot only for security vulnerability alerts (which don't require a dependabot.yml config file). The Renovate config is enhanced with package grouping rules and lock file maintenance scheduling.

Changes:

• Deleted .github/dependabot.yml to stop Dependabot version updates, since Renovate now handles all regular dependency updates
• Updated renovate.json to scope managers to pep621 and github-actions, added grouped package rules for minor/patch Python deps and GitHub Actions, and enabled weekly lock file maintenance
• Removed the dependabot.yml reference from the build chain specification's directory tree

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/dependabot.yml	Fully deleted — Dependabot version updates replaced by Renovate
renovate.json	Expanded config: restricted managers, added grouping rules, lock file maintenance, changed schedule to "at any time"
specifications/SPEC-BUILD-CHAIN-CICD-SERVICE.md	Removed dependabot.yml line from the .github/ directory tree diagram

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.
see 7 files with indirect coverage changes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud