chore(deps): reduce Dependabot update noise

[AgriciDaniel]

This reduces routine Dependabot review volume while keeping major updates available for individual review.

Changes:

• github-actions in /: schedule weekly to monthly, pull-request limit default(5) to 2, groups actions-minor-patch.

Scope is limited to .github/dependabot.yml. No security-update group, CODEOWNERS rule, dependency file, or repository setting changes.

Validation:

• The reviewed patch applies exactly to main at 58e3869605a527c9d952fce193c03ba9a6fc512a and Dependabot blob 5ace4600a1f26e6892982f3e2f069ebfab108d87.
• Duplicate-key-safe YAML validation, policy-field preservation, exact after-file comparison, and git diff --check passed.

Automerge is not enabled. Merge remains subject to review and required checks.