feat(native): add settings screen header component

[v1gneshn]

• Create reusable ScreenHeader component with centered title design
• Integrate header into settings screen to match Figma UI design
• Remove commented-out header code and redundant title text
• Add proper accessibility labels and theme-based styling
• Support optional back button and right action slots for reusability

Fixes #697

Description

Please provide a clear and concise description of the changes made, including
the purpose and context.

Fixes: # (issue number)
or
Resolves: # (issue number)

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Changes Made

• Changes in apps folder (specify the app and briefly describe the
  changes):

  • Web
  • Native

• Changes in packages folder (specify the package and briefly describe
  the changes):

  • Core

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Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing
  functionality to not work as expected)
• 📝 Documentation update (changes)

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Screenshots

Before	After
"screenshot before"	"screenshot after"

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How Has This Been Tested?

• Cypress integration
• Cypress component tests
• Jest unit tests

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Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Additional Comments

(Optional) Add any additional comments or notes for reviewers here.

[pierrelstan]

The header works well here, but since the settings screen is planned to include multiple sub‑screens (account, notifications, etc.), consider updating the _layout.tsx file inside the settings folder. This would allow you to define the header via Stack.Screen options.