chore(runway): cherry-pick fix: Fix transparent defi position nav bar cp-7.73.0 (#28841)

- fix: Fix transparent defi position nav bar cp-7.73.0 (#28833)

<!--
Please submit this PR as a draft initially.
Do not mark it as "Ready for review" until the template has been
completely filled out, and PR status checks have passed at least once.
-->

## **Description**

<!--
Write a short description of the changes included in this pull request,
also include relevant motivation and context. Have in mind the following
questions:
1. What is the reason for the change?
2. What is the improvement/solution?
-->

This ensures that the defi position header has a default background
color, preventing the overlapping header when transitioning via
navigation

## **Changelog**

<!--
If this PR is not End-User-Facing and should not show up in the
CHANGELOG, you can choose to either:
1. Write `CHANGELOG entry: null`
2. Label with `no-changelog`

If this PR is End-User-Facing, please write a short User-Facing
description in the past tense like:
`CHANGELOG entry: Added a new tab for users to see their NFTs`
`CHANGELOG entry: Fixed a bug that was causing some NFTs to flicker`

(This helps the Release Engineer do their job more quickly and
accurately)
-->

CHANGELOG entry:

## **Related issues**

Fixes: https://consensyssoftware.atlassian.net/browse/MCWP-482

## **Manual testing steps**

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
```

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**

<!-- [screenshots/recordings] -->

### **After**

<!-- [screenshots/recordings] -->


<img width="280" height="592" alt="image"

src="https://github.com/user-attachments/assets/5a1d89eb-81c0-470d-bf0f-e596d626f74e"
/>


## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding

Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I've applied the right labels on the PR (see [labeling

guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [x] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [x] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk UI/navigation styling change limited to a single screen; main
risk is unintended visual differences across themes/platforms.
> 
> **Overview**
> Fixes the `DeFiProtocolPositionDetails` stack header rendering by
explicitly setting `headerStyle` (default theme background, no
shadow/elevation) in `MainNavigator`, preventing a
transparent/overlapping navbar during screen transitions.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
22a5f82. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
[67ce7d4](67ce7d4)

Co-authored-by: Cal Leung <cal.leung@consensys.net>

Author: runway-github[bot]

app/components/Nav/Main/MainNavigator.js

@@ -1310,6 +1310,11 @@ const MainNavigator = () => {
         options={({ navigation }) => ({
           ...slideFromRightAnimation,
           ...getDeFiProtocolPositionDetailsNavbarOptions(navigation),
+          headerStyle: {
+            backgroundColor: colors.background.default,
+            shadowColor: importedColors.transparent,
+            elevation: 0,
+          },
         })}
       />
       {