Refactor: remove Python-based Listmonk upgrade logic and implement upgrade as Ansible task

Details:
- Removed upgrade_listmonk() function and related calls from update-docker script
- Added dedicated Ansible task in web-app-listmonk role to run non-interactive DB/schema upgrade
- Conditional execution via MODE_UPDATE

Ref: https://chatgpt.com/share/68bbeff1-27a0-800f-bef3-03ab597595fd

roles/update-docker/templates/script.py.j2

@@ -144,14 +144,6 @@ def update_discourse(directory):
     else:
         print("Discourse update skipped. No changes in git repository.")
 
-def upgrade_listmonk():
-    """
-    Runs the upgrade for Listmonk
-    """
-    print("Starting Listmonk upgrade.")
-    run_command('echo "y" | docker compose run -T application ./listmonk --upgrade')
-    print("Upgrade complete.")
-
 def update_procedure(command):
     """
     Attempts to execute a command up to a maximum number of retries.
@@ -210,8 +202,6 @@ if __name__ == "__main__":
                 # The following instances need additional update and upgrade procedures
                 if os.path.basename(dir_path) == "discourse":
                     update_discourse(dir_path)
-                elif os.path.basename(dir_path) == "listmonk":
-                    upgrade_listmonk()
-                    
+
                 # @todo implement dedicated procedure for bluesky
                 # @todo implement dedicated procedure for taiga