ci: automate Gradle and Docker image updates (#7464)

## Summary

- Add a scheduled GitHub Actions workflow that checks for the latest
stable Gradle release.
- Update the Gradle wrapper and pinned Gradle Docker build images
automatically.
- Open an automated pull request when an update is available.
- Update the developer prerequisites to Node.js 22+ and Gradle 9.0+.

## Details

The workflow runs every Monday at 03:00 UTC and can also be triggered
manually. It:

1. Resolves the latest stable Gradle version.
2. Finds the matching `gradle:<version>-jdk25` Docker image digest.
3. Updates the Gradle wrapper and Dockerfiles.
4. Verifies the resolved wrapper version and checks the resulting diff.
5. Creates or updates an automated dependency pull request.

The current wrapper and Docker image changes are included as the initial
update generated by this workflow.

## Testing

- Verified the generated changes with `git diff --check`.
- The workflow validates the wrapper version before opening the
automated pull request.

.github/workflows/update-gradle.yml

@@ -0,0 +1,112 @@
+name: Update Gradle
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "0 3 * * 1"
+
+concurrency:
+  group: update-gradle
+  cancel-in-progress: true
+
+jobs:
+  update-gradle:
+    name: Update Gradle and Docker images
+    permissions:
+      contents: write
+      pull-requests: write
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Harden runner
+        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        with:
+          egress-policy: audit
+
+      - name: Check out repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - name: Set up Java
+        uses: actions/setup-java@b6effb05e454b25005698d916606bdc6ffcbf961 # v5.7.0
+        with:
+          distribution: temurin
+          java-version: "25"
+
+      - name: Find latest Gradle release
+        id: gradle
+        shell: bash
+        run: |
+          set -euo pipefail
+          version=$(curl --fail --silent --show-error --retry 3 \
+            https://services.gradle.org/versions/current | jq -r '.version')
+          [[ "$version" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]] || {
+            echo "Could not determine a stable Gradle version: $version" >&2
+            exit 1
+          }
+          echo "version=$version" >> "$GITHUB_OUTPUT"
+
+      - name: Find matching Docker image digest
+        id: docker
+        env:
+          GRADLE_VERSION: ${{ steps.gradle.outputs.version }}
+        shell: bash
+        run: |
+          set -euo pipefail
+          tag="${GRADLE_VERSION}-jdk25"
+          digest=$(curl --fail --silent --show-error --retry 3 \
+            "https://hub.docker.com/v2/repositories/library/gradle/tags/${tag}" \
+            | jq -r '.digest // empty')
+          [[ "$digest" =~ ^sha256:[0-9a-f]{64}$ ]] || {
+            echo "Docker image gradle:${tag} was not found" >&2
+            exit 1
+          }
+          echo "tag=$tag" >> "$GITHUB_OUTPUT"
+          echo "digest=$digest" >> "$GITHUB_OUTPUT"
+
+      - name: Update Gradle wrapper
+        env:
+          GRADLE_VERSION: ${{ steps.gradle.outputs.version }}
+        run: ./gradlew wrapper --gradle-version "$GRADLE_VERSION" --distribution-type bin
+
+      - name: Update Gradle Docker images
+        env:
+          DOCKER_TAG: ${{ steps.docker.outputs.tag }}
+          DOCKER_DIGEST: ${{ steps.docker.outputs.digest }}
+        shell: bash
+        run: |
+          set -euo pipefail
+          find docker -type f -name 'Dockerfile*' -print0 |
+            xargs -0 sed -E -i \
+              "s#gradle:[^@[:space:]]+-jdk25(@sha256:[^[:space:]]+)?#gradle:${DOCKER_TAG}@${DOCKER_DIGEST}#g"
+
+      - name: Verify Gradle update
+        env:
+          EXPECTED_VERSION: ${{ steps.gradle.outputs.version }}
+        shell: bash
+        run: |
+          set -euo pipefail
+          actual=$(./gradlew --version | sed -n 's/^Gradle \([0-9.]*\)$/\1/p')
+          [[ "$actual" == "$EXPECTED_VERSION" ]] || {
+            echo "Wrapper resolved Gradle $actual, expected $EXPECTED_VERSION" >&2
+            exit 1
+          }
+          if git diff --quiet; then
+            echo "Gradle is already up to date."
+            exit 0
+          fi
+          git diff --check
+
+      - name: Create pull request
+        uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v8.1.1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          branch: automation/update-gradle
+          delete-branch: true
+          commit-message: "chore: update Gradle"
+          title: "chore: update Gradle to ${{ steps.gradle.outputs.version }}"
+          body: |
+            Automated update of the Gradle wrapper and Gradle Docker build images.
+
+            Gradle version: `${{ steps.gradle.outputs.version }}`
+            Docker image: `gradle:${{ steps.docker.outputs.tag }}`
+          labels: dependencies