ci: add Dependabot cooldown (20260603-170456)

[securityeng-bot]

Add Dependabot cooldown

This PR was generated by sec-cli github dependabot cooldown update.

What changed

A cooldown block has been added to every updates entry in
.github/dependabot.yml that did not already have one.

Example:

updates:
  - package-ecosystem: "go"
    directory: "/"
    schedule:
      interval: "weekly"
    cooldown:
      default-days: 7

Why

The Dependabot cooldown feature delays dependency-update pull requests until a
new version has been available for at least the configured number of days. This
reduces noise from short-lived releases and gives the ecosystem time to catch
regressions before they land in your codebase.