fix(kestra): bake flows into kestra-init image to fix empty /flows in container

Bind mounts don't work on the remote Portainer host since the files
aren't present there. Instead, Dockerfile.init copies the flow YAMLs
into a dedicated image (kestra/kestra:latest base) that is built in CI
and pulled by Portainer like the other images.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/build-and-push.yml

@@ -13,6 +13,7 @@ env:
   BACKEND_IMAGE_NAME: ${{ gitea.repository }}-backend
   FRONTEND_IMAGE_NAME: ${{ gitea.repository }}-frontend
   INTEGRATOR_IMAGE_NAME: ${{ gitea.repository }}-integrator
+  KESTRA_INIT_IMAGE_NAME: ${{ gitea.repository }}-kestra-init
 
 jobs:
   build-backend:
@@ -135,10 +136,47 @@ jobs:
           cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.INTEGRATOR_IMAGE_NAME }}:buildcache
           cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.INTEGRATOR_IMAGE_NAME }}:buildcache,mode=max
 
+  build-kestra-init:
+    name: Build Kestra Init
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Extract metadata for Kestra Init Docker image
+        id: meta-kestra-init
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.KESTRA_INIT_IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=sha,prefix=kestra-init-
+            type=raw,value=latest,enable=${{ gitea.ref == 'refs/heads/main' }}
+
+      - name: Build and push Kestra Init Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: ./integrator
+          file: ./integrator/Dockerfile.init
+          push: ${{ gitea.event_name != 'pull_request' }}
+          tags: ${{ steps.meta-kestra-init.outputs.tags }}
+          labels: ${{ steps.meta-kestra-init.outputs.labels }}
+
   trigger-deployment:
     name: Trigger Portainer Update
     runs-on: ubuntu-latest
-    needs: [build-backend, build-frontend, build-integrator]
+    needs: [build-backend, build-frontend, build-integrator, build-kestra-init]
     if: gitea.event_name != 'pull_request'
     steps:
       - name: Trigger Portainer stack update