CustomCommunication class and streamline SMS logs handling by relying on server-side defaults for columns and rows

[nidh-eesh]

This pull request introduces a backend override for the Communication doctype to provide custom default columns and rows for SMS log listings, and removes redundant frontend logic that previously enforced these defaults. Now, the frontend relies on the backend to supply the correct structure, simplifying the Vue component and centralizing configuration.

Backend enhancements:

• Added a CustomCommunication class in crm/overrides/communication.py that overrides the default columns and rows for the Communication doctype, ensuring consistent structure for SMS logs.
• Registered the new CustomCommunication override in the override_doctype_class mapping in crm/hooks.py.

Frontend simplification:

• Removed the Vue watch and onMounted logic in frontend/src/pages/SmsLogs.vue that previously set default columns and rows for SMS logs, as this is now handled by the backend. [1] [2]