Currency amount display in send flow not intuitive

### What is this about?

When in the mobile send flow, the option to switch between native and fiat currencies is counterintuitive. When I see ETH on the screen, it should be clear that the button allowing me to switch views is either what I'm currently seeing OR what I can switch to seeing. As it appears now, it seems as if the user is seeing ETH when really seeing $, and vice versa. This is particularly an issue when entering the amount I want to send, as it causes frustration if a user begins entering a value with $ in mind and realizes they meant ETH.

### Scenario

_No response_

### Design

https://github.com/user-attachments/assets/b2780ceb-26e4-48be-9225-c2010a9d563a

### 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 response_