[Bug]: Auto-tracking of tokens not working on some networks (Ethereum, Base) - requiring manual addition

**Describe the bug**

Tokens are not being automatically tracked/displayed on certain networks (Ethereum, Base), despite the user having balances. Users must manually add tokens for them to appear. This issue does not affect all networks - Linea appears to be working correctly.

**Expected behavior**

Tokens with existing balances should be automatically tracked and displayed in the token list without requiring manual addition

**Screenshots/Recordings**

https://github.com/user-attachments/assets/e0495146-f31e-43fc-b28e-f6ec9f4b500a
https://github.com/user-attachments/assets/4e0f003f-618a-4ac1-9d2a-175f96b879f6

**Steps to reproduce**

1. Have existing token balances on Ethereum or Base networks
2. Install fresh build 7.62.123 (3445)
3. Navigate to token list for affected networks

**Error messages or log output**

```shell

```

**Where was this bug found?**

Live version (from official store)

**Version**

7.62.123

**Build number**

3445

**Build type**

None

**Device**

iPhone 11

**Operating system**

iOS

**Additional context**

Suspected to be related to a feature flag that may be disabled in the build, preventing auto-tracking functionality. This is the second reported occurrence of this issue.

Note: This issue was discovered while investigating different behavior ("Buy mUSD" CTA visibility based on network selection), which was determined to be expected behavior.

Start by reproducing the missing-token behavior in the token list on Ethereum and Base using build 7.62.123 (3445), comparing it with Linea. Inspect the auto-tracking path and the suspected feature-flag configuration. Done means tokens with existing balances appear automatically on the affected networks without manual addition.

Written by the indexing model from the issue text.