Add cooldown configuration to Dependabot with 7-day delay

[wataru86]

What

• Add cooldown configuration to Dependabot with 7-day delay

[gemini-code-assist]

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[Copilot]

Pull Request Overview

This PR adds cooldown configuration to Dependabot to introduce a 7-day delay between dependency update attempts, helping to reduce noise from frequent updates.

• Added cooldown configuration with 7-day default delay to both package ecosystems
• Applied the same cooldown settings to npm and GitHub Actions package ecosystems

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