[WIP] Add snapshot checker workflow

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Create a pull request in dappnode/DAppNodePackage-geth-generic against main to add/update .github/workflows/snapshot_check.yml implementing the Snapshot Checker workflow.

Set environment variable EXECUTION_CLIENT to geth.

Workflow content must be:

name: Snapshot Checker

on:
  schedule:
    - cron: '0 */6 * * *'
  workflow_dispatch:

jobs:
  snapshot-check-docker:
    runs-on: staking-test-hoodi
    steps:
      - name: Run Snapshot Checker (Docker)
        run: |
          docker run --rm --pull=always \
            -v /var/run/docker.sock:/var/run/docker.sock \
            -v /var/lib/docker/volumes:/var/lib/docker/volumes \
            -e EXECUTION_CLIENT='geth' \
            -e NETWORK=hoodi \
            -e LOG_LEVEL=debug \
            ghcr.io/dappnode/staker-test-util/snapshot-checker:latest

If the file already exists, update only EXECUTION_CLIENT as needed and keep the rest consistent.

PR title: Add snapshot checker workflow.
PR body: mention that the workflow runs the snapshot checker Docker image on a schedule and that EXECUTION_CLIENT=geth.

This pull request was created from Copilot chat.

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