….1 cp-7.70.0 (#27446)

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Standardizes safe area and header inset behavior across the main tab
views (Wallet, Explore, Activity, Rewards).

1. **Reason for the change:** These views used `edges={{ bottom:
'additive' }}` on `SafeAreaView` and `includesTopInset` on headers,
which was inconsistent with the desired layout and could cause double
insets or incorrect safe area handling.
2. **Improvement:** Switched to `edges={{ top: 'additive' }}` on
`SafeAreaView` and removed `includesTopInset` from header components so
the top safe area is handled by the screen container and headers align
consistently.

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CHANGELOG entry: null

Fixes: #27443

```gherkin
Feature: Safe area and header insets on main tabs

  Scenario: Wallet, Explore, Activity, and Rewards use consistent safe area
    Given the app is open on a device or simulator with a notch/safe area

    When the user switches to each main tab (Wallet, Explore, Activity, Rewards)
    Then the top safe area is applied by the screen (no double inset)
    And the header (title + accessories) aligns correctly below the safe area
    And the bottom of each view respects the tab bar / device safe area as before
```

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https://github.com/user-attachments/assets/0eda5978-7bd5-4428-86ea-f62637fb06ed

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https://github.com/user-attachments/assets/a8ff8e19-a49e-41f4-9056-7c2271da8c66

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Layout-only changes to core tab screens
(Wallet/Explore/Activity/Rewards) that can affect safe-area padding and
scroll behavior across devices, plus removal of Wallet’s bottom
fade/scroll tracking logic which could subtly change UX on the homepage.
>
> **Overview**
> Standardizes safe-area handling across the main tab views by switching
root `SafeAreaView` usage from `edges={{ bottom: 'additive' }}` to
`edges={{ top: 'additive' }}` and removing header `includesTopInset` so
the top inset is applied consistently by the screen container.
>
> In `Wallet`, removes the bottom fade `LinearGradient` overlay and its
associated scroll/size tracking state, simplifying scroll handling to
just notify homepage section subscribers via `handleHomepageScroll`.
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
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on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->