[Bug]: Custom networks added from chain list are not accessible correctly

### Describe the bug

Trying to add any custom network (like Chiliz, Bob, Mantle, Stable, etc.) from chainlist adds the network using some RPC url like: lb.routeme.sh/rpc/evm/... with some warning like "According to our records the submitted RPC URL value does not match a known provider for this chain ID."

After adding the network balance is fetched properly, but trying to initiate Send operation displays errors - sometimes wallets hangs, sometimes network error is displayed.

Observed both in Ext and Mobile

### Expected behavior

Custom networks should be added with appropriate RPC urls..

### Screenshots/Recordings

https://github.com/user-attachments/assets/b1fd5979-480f-436d-a333-247d72d04c59

https://github.com/user-attachments/assets/b4367493-6983-4e2e-8cb6-038dc3498752

https://github.com/user-attachments/assets/72f5b4f5-b382-4c7c-9ac0-97f862049641

### Steps to reproduce

- Add any Custom nettwork to your wallet from https://chainlist.org/
- Observe token balance updated
- Try to initiate Send

### Error messages or log output

```shell

```

### Where was this bug found?

Internal release testing

### Version

13.46.0

### Build type

_No response_

### Browser

Chrome

### Operating system

MacOS

### Hardware wallet

_No response_

### Additional context

_No response_

### Severity

_No response_

Reproduce the issue by adding a custom network from chainlist.org, confirming the balance appears, and initiating Send in the extension and mobile experiences. Inspect the custom-network addition and transaction-send flows, using the reported lb.routeme.sh/rpc/evm/... URLs and warning as clues. Done means supported custom networks retain usable RPC URLs and Send no longer hangs or reports a network error.

Written by the indexing model from the issue text.