chore: standardize enterprise Dependabot configuration

[somethingwithproof]

Adds grouped, cooled-down Dependabot updates with standard ecosystem labels and commit prefixes.

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[Copilot]

Pull request overview

This PR introduces GitHub automation configuration intended to standardize dependency update management, and additionally adds a security scanning workflow via CodeQL.

Changes:

• Added a new Dependabot configuration to group GitHub Actions updates, apply a cooldown window, add standard labels, and standardize commit message prefixes.
• Added a new CodeQL workflow to run Ruby analysis on pushes/PRs to selected branches, plus a weekly scheduled scan.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/codeql.yml	Adds a CodeQL analysis workflow (Ruby) triggered on push/PR, schedule, and manual dispatch.
.github/dependabot.yml	Adds a Dependabot v2 config for grouped GitHub Actions dependency updates targeting develop.

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[somethingwithproof]

Both Copilot comments were about the CodeQL workflow (scope creep vs. the Dependabot-only title, and the weekly schedule running on a repo with no Ruby to scan). A prior commit on this branch (chore: keep Dependabot PR focused) already removed .github/workflows/codeql.yml entirely and dropped the npm ecosystem from dependabot.yml, so both points are resolved. Marking threads resolved.