ci/cd: add dependabot and Workflow runs cleanup

.github/actions/notify/action.yml

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+name: Define notification message
+description: Identify an appropriate notification message.
+branding:
+  icon: 'message-square'
+  color: 'green'
+
+inputs:
+  emoji:
+    description: Prefix for the title.
+    default: 🤖
+
+  channel:
+    description: Notification channel.
+    required: true
+
+  success:
+    description: Is the result successful?
+    required: true
+    default: 'true'
+
+runs:
+  using: composite
+  steps:
+    - name: Define notification message
+      id: message
+      run: |
+        if [ '${{ github.event.head_commit.message != null }}' == 'true' ]
+        then
+          (cat <<-message
+        txt=${{ github.event.head_commit.message }}
+        message
+        ) | head -1 >> $GITHUB_OUTPUT
+
+        elif [ '${{ github.event.inputs.reason != null }}' == 'true' ]
+        then
+          (cat <<-message
+        txt=${{ github.event.inputs.reason }}
+        message
+        ) | head -1 >> $GITHUB_OUTPUT
+
+        elif [ '${{ github.event.schedule != null }}' == 'true' ]
+        then
+          echo txt='regular healthcheck' >> $GITHUB_OUTPUT
+        else
+          echo Cannot define notification message && exit 1
+        fi
+      shell: bash
+
+    - name: Send Slack notification
+      uses: rtCamp/action-slack-notify@v2
+      env:
+        SLACK_COLOR: ${{ inputs.success == 'true' && 'success' || 'failure' }}
+        SLACK_FOOTER: made with ❤️ for everyone by <https://www.octolab.org/|OctoLab>
+        SLACK_ICON: https://cdn.octolab.org/geek/octolab.png
+        SLACK_MESSAGE: ${{ steps.message.outputs.txt }}
+        SLACK_TITLE: '${{ inputs.emoji }} ${{ github.repository }}: ${{ github.workflow }}'
+        SLACK_USERNAME: Notifier
+        SLACK_WEBHOOK: ${{ inputs.channel }}

.github/dependabot.yml

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+version: 2
+
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: daily
+      time: '05:00'
+      timezone: UTC
+    labels:
+      - 'type: improvement'
+      - 'scope: inventory'
+      - 'scope: deps'
+    commit-message:
+      prefix: 'ci/cd'
+      include: 'scope'
+    open-pull-requests-limit: 30
+
+  - package-ecosystem: docker
+    directory: /
+    schedule:
+      interval: daily
+      time: '05:00'
+      timezone: UTC
+    labels:
+      - 'type: improvement'
+      - 'scope: inventory'
+      - 'scope: deps'
+    commit-message:
+      prefix: 'ci/cd'
+      include: 'scope'
+    open-pull-requests-limit: 30

.github/workflows/cleanup.runs.yml

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+name: Workflow runs cleanup
+
+on:
+  schedule:
+    - cron: 0 6 1 * * # at 06:00 on day-of-month 1, UTC
+
+  workflow_dispatch:
+    inputs:
+      pattern:
+        description: The name of workflow to clean.
+        type: choice
+        options:
+          - All
+          - Continuous delivery
+          - Workflow runs cleanup
+        default: Workflow runs cleanup
+        required: true
+      dry_run:
+        description: Only log actions, do not perform any delete operations.
+        type: boolean
+        required: false
+      reason:
+        description: The reason for dispatching it manually.
+        type: string
+        default: manual healthcheck
+        required: true
+
+jobs:
+  delete:
+    name: Deleting
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Delete workflow runs
+        uses: Mattraks/delete-workflow-runs@v2
+        with:
+          token: ${{ github.token }}
+          repository: ${{ github.repository }}
+          delete_workflow_pattern: ${{ github.event.inputs.pattern || 'all' }}
+          dry_run: ${{ fromJSON('["", "true"]')[github.event.inputs.dry_run == 'true'] }}
+          retain_days: 0
+          keep_minimum_runs: 0
+
+  notify:
+    name: Notifying
+    needs: [ delete ]
+    runs-on: ubuntu-latest
+    if: failure() || success()
+
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+
+      - name: Send notification
+        uses: ./.github/actions/notify
+        continue-on-error: true
+        with:
+          emoji: 🧹
+          channel: ${{ secrets.SLACK_WEBHOOK }}
+          success: ${{ ! contains(needs.*.result, 'failure') }}