fix: increase terragrunt-apply step memory to 2Gi

LimitRange defaults containers to 192Mi which is insufficient for
terragrunt apply on the platform stack (48 vault refs, many modules).
Set explicit 1Gi request / 2Gi limit via backend_options.

.woodpecker/default.yml

@@ -28,6 +28,13 @@ steps:
 
   - name: terragrunt-apply
     image: alpine
+    backend_options:
+      kubernetes:
+        resources:
+          requests:
+            memory: 1Gi
+          limits:
+            memory: 2Gi
     commands:
       - "apk update && apk add curl unzip git openssh-client"
       # Install Terraform