fix(release): restrict production workflows to v4.x

Update release documentation and workflow coverage tests for the branch strategy.

.github/workflows/coolify-helper.yml

@@ -2,7 +2,7 @@ name: Coolify Helper Image
 
 on:
   push:
-    branches: [ "v4.x", "main" ]
+    branches: [ "v4.x" ]
     paths:
       - .github/workflows/coolify-helper.yml
       - docker/coolify-helper/Dockerfile
@@ -113,4 +113,3 @@ jobs:
         if: always()
         with:
           webhook: ${{ secrets.DISCORD_WEBHOOK_PROD_RELEASE_CHANNEL  }}
-