Add GitHub Actions workflow for Docker image release

This workflow automates building and publishing Docker images upon a release or manual trigger. It includes steps for version resolution, Docker Hub login, and caching to optimize builds for both backend and frontend images.

.github/workflows/docker-release.yml

@@ -0,0 +1,91 @@
+name: Docker Publish (Release)
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+    inputs:
+      version:
+        description: "Version tag to publish (e.g. 0.1.2 or v0.1.2)"
+        required: false
+        type: string
+
+jobs:
+  publish:
+    name: Build and Push Docker Images
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+
+    env:
+      # Optional repo variable. If unset, DOCKERHUB_USERNAME is used.
+      IMAGE_NAMESPACE: ${{ vars.DOCKERHUB_NAMESPACE }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Resolve version/tag
+        id: ver
+        shell: bash
+        run: |
+          RAW_TAG="${{ github.event.release.tag_name }}"
+          if [ -z "$RAW_TAG" ]; then
+            RAW_TAG="${{ inputs.version }}"
+          fi
+          if [ -z "$RAW_TAG" ]; then
+            RAW_TAG="${GITHUB_REF_NAME}"
+          fi
+
+          CLEAN_TAG="${RAW_TAG#v}"
+          echo "raw=$RAW_TAG" >> "$GITHUB_OUTPUT"
+          echo "clean=$CLEAN_TAG" >> "$GITHUB_OUTPUT"
+
+      - name: Set image namespace
+        id: ns
+        shell: bash
+        run: |
+          NS="${IMAGE_NAMESPACE}"
+          if [ -z "$NS" ]; then
+            NS="${{ secrets.DOCKERHUB_USERNAME }}"
+          fi
+          if [ -z "$NS" ]; then
+            echo "Missing Docker Hub namespace. Set repo var DOCKERHUB_NAMESPACE or secret DOCKERHUB_USERNAME."
+            exit 1
+          fi
+          echo "value=$NS" >> "$GITHUB_OUTPUT"
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push backend image
+        uses: docker/build-push-action@v6
+        with:
+          context: ./backend
+          file: ./backend/Dockerfile
+          push: true
+          tags: |
+            ${{ steps.ns.outputs.value }}/nexapg-backend:${{ steps.ver.outputs.clean }}
+            ${{ steps.ns.outputs.value }}/nexapg-backend:latest
+          cache-from: type=registry,ref=${{ steps.ns.outputs.value }}/nexapg-backend:buildcache
+          cache-to: type=registry,ref=${{ steps.ns.outputs.value }}/nexapg-backend:buildcache,mode=max
+
+      - name: Build and push frontend image
+        uses: docker/build-push-action@v6
+        with:
+          context: ./frontend
+          file: ./frontend/Dockerfile
+          push: true
+          build-args: |
+            VITE_API_URL=/api/v1
+          tags: |
+            ${{ steps.ns.outputs.value }}/nexapg-frontend:${{ steps.ver.outputs.clean }}
+            ${{ steps.ns.outputs.value }}/nexapg-frontend:latest
+          cache-from: type=registry,ref=${{ steps.ns.outputs.value }}/nexapg-frontend:buildcache
+          cache-to: type=registry,ref=${{ steps.ns.outputs.value }}/nexapg-frontend:buildcache,mode=max