feat: add validation for production SSH credentials in deployment workflow

.gitea/workflows/promote-master.yaml

@@ -353,6 +353,15 @@ jobs:
               exit 1
             fi
 
+            # Validate that MONGO_URI is present (falling back to previous .env if available)
+            if [ -z "${{ secrets.MONGO_URI }}" ]; then
+                echo "ERROR: MONGO_URI secret is missing or empty in Gitea repository secrets."
+                exit 1
+              fi
+            else
+              echo "MONGO_URI successfully loaded from Gitea secrets."
+            fi
+
             cat > .env << EOF
             FRONTEND_URL=${{ secrets.PROD_FRONTEND_URL }}
             BACKEND_HOST_PORT=${{ secrets.PROD_BACKEND_HOST_PORT }}