fix(settings): render Attach field name when value is a dict

[walidsaleh]

Summary

Fix the generic SettingFields.vue template so it renders the file name of an Attach / AttachImage field even when the value is a dict (as returned by frappe.get_doc().as_dict()), not just a string.

This unblocks editing for any settings modal that uses SettingFields and has a previously-saved Attach field, e.g. Payment Gateway.header_img, Website Settings.banner_image.

Fixes #2417

Changes

One-line guard in frontend/src/components/Settings/SettingFields.vue:63:

<!-- before -->
{{ data[field.name].split('/').pop() }}

<!-- after -->
{{ typeof data[field.name] === 'string'
    ? data[field.name].split('/').pop()
    : (data[field.name]?.file_name || '') }}

Why

frappe.get_doc(...).as_dict() (used by lms.lms.api.get_payment_gateway_details and similar endpoints) serializes Attach / AttachImage fields as objects with file_url, file_name, file_size, etc. The template was assuming a string and calling .split unconditionally, which threw on the first open of any settings modal that had a saved Attach field, breaking the entire modal.

Test plan

• Open Desk → Payment Gateway → edit a gateway that has a logo uploaded. Modal should render without throwing, and the filename should be visible.
• Open LMS Settings → any tab that has an Attach field. Should render without throwing.
• Open a fresh modal, upload a new file. The new file URL should be visible in the preview (existing behaviour, preserved).

[raizasafeel]

Hey, could you lint the code as per contribution guidelines:
https://github.com/frappe/erpnext/wiki/Pull-Request-Checklist#linting