Allow user to dismiss "Fund your wallet" banner

### What is this about?

As a user with an empty account, I want to be able to dismiss the "Fund your wallet" banner with a close icon or dismiss button.

Since it is a promotional type banner and user can always use the "Buy" CTA we could allow users to dismiss.

### Scenario

_No response_

### Design

_No response_

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References


No files, tests, or entry points are named. Search the extension UI for the “Fund your wallet” banner and inspect its existing “Buy” CTA; confirm the relevant product or design expectation, then verify that an empty-account user can dismiss the promotional banner with the requested control.

Written by the indexing model from the issue text.