ci: dev/stage/main branch build pipeline for custom Gitea image

Build and push to Artifact Registry on merge to dev/stage/main:
  dev   → gitea:dev
  stage → gitea:stage
  main  → gitea:latest + gitea:<sha>

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

.gitea/workflows/build-push.yaml

@@ -1,9 +1,17 @@
 name: Build & Push Gitea image
 
+# Builds and pushes a custom Gitea image to Artifact Registry.
+# Branch → image tag mapping:
+#   dev   → gitea:dev   (inner dev loop)
+#   stage → gitea:stage (staging verification)
+#   main  → gitea:latest + gitea:<sha> (production)
+
 on:
   push:
     branches:
-      - feat/workflow-step-events
+      - dev
+      - stage
+      - main
   workflow_dispatch:
 
 jobs:
@@ -30,30 +38,52 @@ jobs:
       - name: Configure Docker for Artifact Registry
         run: gcloud auth configure-docker us-central1-docker.pkg.dev --quiet
 
-      - name: Set image tag
+      - name: Compute image tags
         id: tag
         run: |
+          REGISTRY="us-central1-docker.pkg.dev/neuron-785695/neuron-ci/gitea"
           SHA="${GITHUB_SHA:0:8}"
-          echo "tag=us-central1-docker.pkg.dev/neuron-785695/neuron-ci/gitea:${SHA}" >> "$GITHUB_OUTPUT"
-          echo "latest=us-central1-docker.pkg.dev/neuron-785695/neuron-ci/gitea:latest" >> "$GITHUB_OUTPUT"
-          echo "SHA=${SHA}" >> "$GITHUB_OUTPUT"
+          BRANCH="${GITEA_REF_NAME:-${GITHUB_REF_NAME}}"
+          case "$BRANCH" in
+            main)
+              TAGS="${REGISTRY}:latest ${REGISTRY}:${SHA}"
+              ENV_TAG="latest"
+              ;;
+            stage)
+              TAGS="${REGISTRY}:stage ${REGISTRY}:stage-${SHA}"
+              ENV_TAG="stage"
+              ;;
+            dev)
+              TAGS="${REGISTRY}:dev ${REGISTRY}:dev-${SHA}"
+              ENV_TAG="dev"
+              ;;
+            *)
+              TAGS="${REGISTRY}:${SHA}"
+              ENV_TAG="${SHA}"
+              ;;
+          esac
+          echo "tags=${TAGS}" >> "$GITHUB_OUTPUT"
+          echo "primary=${REGISTRY}:${ENV_TAG}" >> "$GITHUB_OUTPUT"
+          echo "sha=${SHA}" >> "$GITHUB_OUTPUT"
 
       - name: Build Gitea image
         run: |
+          TAGS=""
+          for t in ${{ steps.tag.outputs.tags }}; do
+            TAGS="$TAGS -t $t"
+          done
           docker build \
             --build-arg GITEA_VERSION="neuron-$(git rev-parse --short HEAD)" \
             --build-arg TAGS="sqlite sqlite_unlock_notify" \
-            -t "${{ steps.tag.outputs.tag }}" \
-            -t "${{ steps.tag.outputs.latest }}" \
+            $TAGS \
             .
 
       - name: Push Gitea image
         run: |
-          docker push "${{ steps.tag.outputs.tag }}"
-          docker push "${{ steps.tag.outputs.latest }}"
-          echo "Pushed gitea:${{ steps.tag.outputs.SHA }} and :latest"
+          for t in ${{ steps.tag.outputs.tags }}; do
+            docker push "$t"
+            echo "Pushed: $t"
+          done
 
-      - name: Output image tag
-        run: |
-          echo "::notice title=Image pushed::${{ steps.tag.outputs.tag }}"
-          echo "Update deployment.yaml image to: ${{ steps.tag.outputs.tag }}"
+      - name: Output
+        run: echo "::notice title=Image::${{ steps.tag.outputs.primary }}"