fix(ci): fix YAML parse error in deploy workflow caused by inner heredoc

The compose file was written via a bash << 'COMPOSE' heredoc nested inside
the YAML run: | block scalar. Lines like "name: petloft-staging" at column 0
cause the YAML parser to break out of the block scalar early, making the
entire workflow file invalid YAML — Gitea silently drops invalid workflows,
so no jobs triggered at all.

Fix: move compose.yml to deploy/staging/compose.yml in the repo, substitute
${REGISTRY} on the runner, base64-encode the result, and decode it on the VPS
inside the SSH session. No inner heredoc needed.

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

.gitea/workflows/deploy-staging.yml

@@ -159,6 +159,8 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - uses: actions/checkout@v4
+
       - name: Write SSH key
         run: |
           mkdir -p ~/.ssh
@@ -174,9 +176,14 @@ jobs:
           SSH_USER: ${{ secrets.STAGING_SSH_USER }}
           SSH_PORT: ${{ secrets.STAGING_SSH_PORT }}
         run: |
-          # Auth key is the hostname only — strip the /owner path
           REGISTRY_HOST=$(echo "$REGISTRY" | cut -d'/' -f1)
 
+          # Substitute the actual registry value and base64-encode the compose file.
+          # Passing it as a base64 string through the SSH heredoc avoids the need for
+          # an inner heredoc, which breaks YAML parsing when compose content has lines
+          # at column 0 (YAML sees them as new top-level nodes, invalidating the file).
+          COMPOSE_B64=$(sed "s|\${REGISTRY}|${REGISTRY}|g" deploy/staging/compose.yml | base64 -w 0)
+
           # StrictHostKeyChecking=accept-new trusts on first connect but rejects
           # changed keys on subsequent runs — safer than no-verify
           ssh -i ~/.ssh/staging \
@@ -196,37 +203,10 @@ jobs:
 
           mkdir -p /opt/staging
 
-          # Write the compose file on every deploy so it stays in sync with CI.
-          # REGISTRY is interpolated by bash here (not by podman compose), so the
-          # actual registry host:port/owner value is embedded in the file.
-          cat > /opt/staging/compose.yml << 'COMPOSE'
-name: petloft-staging
-
-services:
-  storefront:
-    image: ${REGISTRY}/storefront:staging
-    restart: unless-stopped
-    ports:
-      - "3000:3000"
-    env_file:
-      - path: .env
-        required: false
-
-  admin:
-    image: ${REGISTRY}/admin:staging
-    restart: unless-stopped
-    ports:
-      - "3001:3001"
-    env_file:
-      - path: .env
-        required: false
-COMPOSE
-          # Substitute the actual registry value into the compose file
-          sed -i "s|\${REGISTRY}|${REGISTRY}|g" /opt/staging/compose.yml
-
-          # Create a minimal .env if one doesn't exist.
+          # Decode the compose file that was base64-encoded on the runner.
           # Runtime secrets (CLERK_SECRET_KEY, etc.) should be added manually
           # to /opt/staging/.env on the VPS after first deploy.
+          echo "${COMPOSE_B64}" | base64 -d > /opt/staging/compose.yml
           touch /opt/staging/.env
 
           cd /opt/staging