[Bug]: Transactions stuck or dropped when sending small or near-maximum fiat amounts via browser extension

**Describe the bug**

When sending ETH via the browser extension (Chrome) using fiat input, transactions can become stuck in pending or get dropped later. This happens when:

- Entering a very small amount in fiat (e.g., $0.01 USD)
- Entering an amount in fiat close to the maximum available value

Once such a transaction is initiated, it does not reach the blockchain, and after some time (up to a week), it is marked as dropped.

All subsequent transactions fail as well, until the account is recovered.

Example dropped transaction on Optimism:
https://optimistic.etherscan.io/tx/0xbfa0798126f6f14ee25a206a99abe9498a5f56f3b591385da36871f3f7dbd126

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**Notes:**
- Happens only when sending in fiat mode
- Reproduced consistently on Optimism

**Expected behavior**

Transaction is broadcast and mined successfully.

Actual:
- Transaction stays in pending or gets dropped
- Subsequent transactions also fail
- Only way to fix is recovering the account

**Screenshots/Recordings**

**Visual Evidence:**
- Video reproduction: *attached*
- Screenshot of stuck/dropped transaction:

https://github.com/user-attachments/assets/c5452fb3-177a-4385-9107-a77f1aa1839c

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**Steps to reproduce**

1. Open the browser extension (Chrome).
2. Go to Send.
3. Choose fiat input and enter either:
- A very small value (e.g., $0.01 USD)
- Or an amount close to the maximum available balance
4. Confirm the transaction.

**Error messages or log output**

```shell

```

**Detection stage**

In production (default)

**Version**

unknown

**Build type**

None

**Browser**

Chrome

**Operating system**

Other (please elaborate in the "Additional Context" section)