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

DeveloperGuide.md

@@ -46,8 +46,8 @@ This guide focuses on developing for Stirling 2.0, including both the React fron
 - Docker
 - Git
 - Java JDK 25
-- Node.js 18+ and npm (required for frontend development)
-- Gradle 7.0 or later (Included within the repo)
+- Node.js 22+ and npm (required for frontend development)
+- Gradle 9.0 or later (Included within the repo)
 - [uv](https://docs.astral.sh/uv/) — Python package manager (required for engine development)
 - Rust and Cargo (required for Tauri desktop app development)
 - Tauri CLI (install with `cargo install tauri-cli`)

docker/backend/Dockerfile

@@ -4,7 +4,7 @@ ARG BASE_VERSION=1.0.2@sha256:c7698687f486707ddef9e0298587ca8b44c4e96185e1bdb0c3
 ARG BASE_IMAGE=stirlingtools/stirling-pdf-base:${BASE_VERSION}
 
 # Stage 1: Build the Java application (backend only, no frontend)
-FROM gradle:9.6.1-jdk25@sha256:e8aeffb8197b17151ce24607811f60e91125f0018f7a3b08dc504ba9168a9c4f AS app-build
+FROM gradle:9.7.0-jdk25@sha256:7d4e63b32991e679b183645680ff81762b6f1ef137850d8c2750b362eb994d08 AS app-build
 
 # JDK 25+: --add-exports is no longer accepted via JAVA_TOOL_OPTIONS; use JDK_JAVA_OPTIONS instead
 ENV JDK_JAVA_OPTIONS="--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED \

docker/embedded/Dockerfile

@@ -5,7 +5,7 @@ ARG BASE_VERSION=1.0.2@sha256:c7698687f486707ddef9e0298587ca8b44c4e96185e1bdb0c3
 ARG BASE_IMAGE=stirlingtools/stirling-pdf-base:${BASE_VERSION}
 
 # Stage 1: Build the Java application and frontend
-FROM gradle:9.6.1-jdk25@sha256:e8aeffb8197b17151ce24607811f60e91125f0018f7a3b08dc504ba9168a9c4f AS app-build
+FROM gradle:9.7.0-jdk25@sha256:7d4e63b32991e679b183645680ff81762b6f1ef137850d8c2750b362eb994d08 AS app-build
 
 ARG TASK_VERSION=3.52.0
 RUN apt-get update \

docker/embedded/Dockerfile.fat

@@ -6,7 +6,7 @@ ARG BASE_VERSION=1.0.2@sha256:c7698687f486707ddef9e0298587ca8b44c4e96185e1bdb0c3
 ARG BASE_IMAGE=stirlingtools/stirling-pdf-base:${BASE_VERSION}
 
 # Stage 1: Build the Java application and frontend
-FROM gradle:9.6.1-jdk25@sha256:e8aeffb8197b17151ce24607811f60e91125f0018f7a3b08dc504ba9168a9c4f AS app-build
+FROM gradle:9.7.0-jdk25@sha256:7d4e63b32991e679b183645680ff81762b6f1ef137850d8c2750b362eb994d08 AS app-build
 
 ARG TASK_VERSION=3.52.0
 RUN apt-get update \

docker/embedded/Dockerfile.ultra-lite

@@ -2,7 +2,7 @@
 # Single JAR contains both frontend and backend with minimal dependencies
 
 # Stage 1: Build application with embedded frontend
-FROM gradle:9.6.1-jdk25@sha256:e8aeffb8197b17151ce24607811f60e91125f0018f7a3b08dc504ba9168a9c4f AS build
+FROM gradle:9.7.0-jdk25@sha256:7d4e63b32991e679b183645680ff81762b6f1ef137850d8c2750b362eb994d08 AS build
 
 # Install Node.js and npm for frontend build
 ARG TASK_VERSION=3.52.0

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.6.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.7.0-bin.zip
 networkTimeout=10000
 retries=0
 retryBackOffMs=500