chore: Add Dependabot version-update cooldown

[ld-repository-standards]

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• Ensure every entry under updates in .github/dependabot.yml declares a cooldown of at least 7 days (default-days).
• Add entries for detected package ecosystems that were not yet tracked by Dependabot.

Cooldown applies only to version updates; security updates bypass it, so critical CVE fixes are never delayed.

Ref: SEC-8058.

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Note

Low Risk
CI/dependency automation only; no application runtime changes, and security updates bypass the cooldown.

Overview
Introduces .github/dependabot.yml to automate dependency updates across the monorepo’s many package roots (npm, gomod, bundler, cargo, gradle, maven, pip, nuget, docker, github-actions, and others).

Every updates entry uses a weekly schedule and cooldown.default-days: 7, so routine version bumps are spaced out; security updates are not subject to this cooldown and can still land immediately.

The config also adds Dependabot tracking for ecosystems/directories that were detected in the repo but not previously listed.

^{Reviewed by Cursor Bugbot for commit e0eab4e. Bugbot is set up for automated code reviews on this repo. Configure here.}