Add Payment Defaults for User

[vatsaaaal]

Description

This PR implements the second option from the proposed solutions in Issue #449. Users can now save their bank details as global defaults, which will automatically populate the invoice form, streamlining the process. Additionally, the "Save as Default" button allows users to store bank details, while the dropdown provides easy access to select and manage previously saved details.

1. Added a "Save as Default" button in the invoice form under the "Bank Details" section.
2. Implemented a dropdown that allows users to select from their saved bank details.
3. Integrated the feature into the Settings page to provide global default options for future invoices.

Checklist

• Ran the Black Formatter and
  djLint-er on any new code
  (checks
  will
  fail without)
• Made any changes or additions to the documentation where required
• Changes generate no new warnings/errors
• New and existing unit tests pass locally with my
  changes

What type of PR is this?

• ✨ Feature

Added/updated tests?

• 🙅 no, because they aren't needed

Related PRs, Issues etc

• Related Issue idea: Add payment details to Settings page as a default option #449
• Closes idea: Add payment details to Settings page as a default option #449