chore: standardize npm dependabot config with dev/prod groups

[willfarrell]

Summary

Apply consistent dependabot npm configuration across repos:

  - package-ecosystem: npm
    directory: "/"
    schedule:
      interval: "weekly"
    cooldown-period: 15
    groups:
      dev-dependencies:
        dependency-type: "development"
        update-types:
          - "minor"
          - "patch"
      prod-dependencies:
        dependency-type: "production"
        update-types:
          - "patch"

• Group dev dependencies (minor + patch) and prod dependencies (patch only) into batched PRs
• Use cooldown-period: 15 days consistently (was previously missing, cooldown-period: 15, or nested cooldown: default-days: 15)

Test plan

• Verify dependabot parses config without errors
• Verify next dependabot run produces grouped dev-dependencies / prod-dependencies PRs