fix: add backend health check step to production workflow

Add "Wait for backend health" step using docker exec to verify backend
is responding before attempting external health check. Matches staging
workflow pattern.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/production.yaml

@@ -296,6 +296,22 @@ jobs:
             fi
           done
 
+      - name: Wait for backend health
+        run: |
+          for i in 1 2 3 4 5 6; do
+            if docker exec mvp-backend-$TARGET_STACK curl -sf http://localhost:3001/health > /dev/null 2>&1; then
+              echo "OK: Backend health check passed"
+              exit 0
+            fi
+            if [ $i -eq 6 ]; then
+              echo "ERROR: Backend health check failed after 6 attempts"
+              docker logs mvp-backend-$TARGET_STACK --tail 100
+              exit 1
+            fi
+            echo "Attempt $i/6: Backend not ready, waiting 10s..."
+            sleep 10
+          done
+
       - name: External health check
         run: |
           REQUIRED_FEATURES='["admin","auth","onboarding","vehicles","documents","fuel-logs","stations","maintenance","platform","notifications","user-profile","user-preferences","user-export"]'