ci: allow Dependabot to group updates across ecosystems

[triceo]

Description of the change

Description here

Checklist

Development

• The changes have been covered with tests, if necessary.
• You have a green build, with the exception of the flaky tests.
• UI and JS files are fully tested, the user interface works for all modules affected by your changes (e.g., solve and analyze buttons).
• The network calls work for all modules affected by your changes (e.g., solving a problem).
• The console messages are validated for all modules affected by your changes.

Code Review

• This pull request includes an explanatory title and description.
• The GitHub issue is linked.
• At least one other engineer has approved the changes.
• After PR is merged, inform the reporter.

[Copilot]

Pull Request Overview

This PR reconfigures Dependabot to use a multi-ecosystem group for Maven, Gradle, and GitHub Actions updates and centralizes registry settings.

• Adds a custom Maven Artifactory registry under registries
• Defines a multi-ecosystem-groups.quickstarts block to group all updates
• Updates individual updates entries to reference the quickstarts group

Comments suppressed due to low confidence (2)

.github/dependabot.yml:11

• The quickstarts group currently only specifies schedule; it lacks a target-branch: "development" setting, so Dependabot will open PRs against the default branch instead of development.

  quickstarts:

.github/dependabot.yml:21

• The registries field should be a list rather than a string. Use registries: ["*"] to allow matching multiple registries.

    registries: "*"