feat: Add Dependabot auto-merge workflow

[Marenz]

This PR adds a GitHub workflow to automatically manage Dependabot pull requests.

This workflow uses the ad/dependabot-auto-approve@v1 GitHub Action, which may need to be explicitly whitelisted in the organization's settings.

[Copilot]

Pull Request Overview

Adds a workflow to automatically approve and merge Dependabot pull requests.

• Introduces a GitHub Actions workflow gated to Dependabot actor.
• Configures auto-approval, labeling, and merge behavior for all dependency types.

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[Copilot]

[nitpick] Using on: pull_request without restricting event types causes the workflow to be evaluated for every pull request (then skipped via the if condition), creating unnecessary workflow invocations. Restrict with types: [opened, synchronize, reopened] or use pull_request_target if appropriate.

Suggested change

	on: pull_request
	on:
	pull_request:
	types: [opened, synchronize, reopened]

[Copilot]

[nitpick] Auto-merging all dependency types increases risk of merging breaking major updates or dev-only changes without review. Consider narrowing to 'production' or adding a versioning strategy (e.g., limiting to patch/minor) to reduce disruption.

Suggested change

	dependency-type: 'all'
	dependency-type: 'production'

[llucax]

I like it, but this is probably not the best repository to add this to, because grpc/protobuf updates need manual intervention.

So I would add this as is to some other, non-API, repo first, and after this one is working, we can consider doing one or more of these:

1. Add a feature to the auto-merge action to only auto-approve PRs that matches some regex (so we can exclude the protobuf/grpc stuff)
2. Add some step/workflow to automatically fix the protobuf /grpc updates.
3. Disable protobuf/grpc updates and find another way to update those, normally we should probably only change these dependencies for major updates, there is not harm in supporting older versions, except maybe for patch updates, maybe for those we really want to re-generate the python files. But is something that needs more thought.

[llucax]

Marking as needs changes to avoid accidental merges, as merging this will be problematic if protobuf/grpc bumps are automatically merged.