feat: add actions/cache and Docker layer caching

- actions/cache@v4 for node_modules across unit-tests and build jobs
- Manual sha256sum key since Gitea lacks hashFiles() support
- Docker BuildKit registry-based cache layers (--cache-from/--cache-to)
- Both runners configured with their own cache server ports

.gitea/workflows/release.yml

@@ -109,9 +109,13 @@ jobs:
 
       - name: Build test-capable image
         if: steps.commit.outputs.committed == 'true'
+        env:
+          DOCKER_BUILDKIT: 1
         run: |
           docker build \
             --target test-runner \
+            --cache-from type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:cache-test \
+            --cache-to type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:cache-test,mode=max \
             --build-arg GIT_COMMIT=${{ github.sha }} \
             -t ${{ env.IMAGE_NAME }}-test:${{ steps.version.outputs.new_version }} \
             .
@@ -127,9 +131,13 @@ jobs:
 
       - name: Build production image
         if: steps.commit.outputs.committed == 'true'
+        env:
+          DOCKER_BUILDKIT: 1
         run: |
           docker build \
             --target runner \
+            --cache-from type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:cache \
+            --cache-to type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:cache,mode=max \
             --build-arg GIT_COMMIT=${{ github.sha }} \
             -t ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.version.outputs.new_version }} \
             -t ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest \