[Bug]: Earn - Supply USDC allows to customize Approval amount potentially leading to the 2nd transaction to fail

### Describe the bug

Supply USDC allows to customize Approval amount potentially leading to the 2nd transaction to fail, if the user edits the approval amount to a smaller value

### Expected behavior

We shouldn't allow the user to edit the approval amount (at least to a smaller value than the one we intend to supply)?

### Screenshots/Recordings

https://github.com/user-attachments/assets/0b3c1f7e-370f-4613-8552-b5da3c90d67c

### Steps to reproduce

1. Have some USDC in Arbitrum
2. Click Earn
3. Add amount ie 10$
4. Click Approve
5. Edit the approve amount to 1$
6. Confirm
7. Click second transaction
8. See you cannot confirm it as it will fail (the fee is super high because of this other bug https://github.com/MetaMask/metamask-mobile/issues/29847)

### Error messages or log output

```shell

```

### Where was this bug found?

Internal release testing

### Version

7.76.0 but seems it might be in prod if that's enabled there too

### Build number

4829

### Build type

None

### Device

Pixel 6

### Operating system

Android

### Additional context

_No response_

### Severity

_No response_

Start at the Earn flow and reproduce the USDC approval sequence on Arbitrum using the steps in the issue. Check how the approval amount is exposed before the second transaction; done means a user cannot reduce it below the intended supply amount and the follow-up transaction remains confirmable.

Written by the indexing model from the issue text.