Polish Settings UI layout and copy

[designerzhi]

Description

Summary

This PR focuses on Settings UI polish and copy cleanup only. It does not change persistence behavior or backend logic.

Changes

• Refined the About page layout:

  • expands the About card to fill the available space
  • centers MicroClaw version/update content
  • moves Copyright into the bottom of the card

• Improved Privacy settings copy and structure:

  • renamed chat history action row to “Clear all chat history”
  • changed action button to “Clear”
  • clarified Sensitive file access as a built-in permission safeguard

• Improved Security settings wording:

  • renamed “Folder access” to “Sandbox folder access”
  • shortened the description to make it clearly part of Security sandbox

• Polished Channels settings:

  • removed the bulky WeChat icon background in embedded Settings view
  • reduced row height

• Polished General settings:

  • fixed Language selector chevron spacing
  • moved Gateway connection status into the section header
  • renamed action rows to “Restart Gateway” and “Export Gateway logs”

• Polished Usage settings:

  • changed Refresh from a bordered text button to a lightweight icon button

Validation

• Verified changed files have no editor-reported errors.
• Checked the updated Settings screens in local browser preview.

Related Issue

Changes

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• CI/CD or build configuration change
• Refactoring (no functional changes)

Testing

• Tests pass locally (cd desktop && npm run test)
• Renderer tests pass locally (cd desktop/renderer && npm run test)
• Build succeeds (cd desktop && npm run build)
• Manual testing performed (describe below)

Checklist

• My code follows the coding guidelines of this project
• I have performed a self-review of my code
• I have commented my code where necessary
• 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 my feature works
• New and existing unit tests pass locally with my changes