feat: allow import settings in initial welcome screen

[roomote]

Related GitHub Issue

Closes: #10992

Description

This PR attempts to address Issue #10992 by adding an "Import Settings" link to the welcome landing screen.

Implementation Details:

• Added a new VSCodeLink component to the landing screen (WelcomeViewProvider.tsx)
• The link triggers the existing importSettings message handler: vscode.postMessage({ type: "importSettings" })
• Uses the existing translation key welcome:importSettings which is already available in the locales
• Placed below the main CTA buttons as a secondary action to maintain visual hierarchy

Benefits:

• Minimal code change (8 lines added)
• Reuses existing import infrastructure and translations
• Does not disrupt the existing welcome flow for new users
• Addresses both use cases: individual migrations and enterprise standardization

Test Procedure

1. Install the extension on a fresh VS Code setup (or clear existing Roo Code settings)
2. Open VS Code and trigger the Roo Code extension
3. Verify the welcome landing screen shows the "Import Settings" link below the main action buttons
4. Click the "Import Settings" link
5. Verify the file picker opens allowing you to select a settings file
6. Select a valid settings file and verify the import works correctly

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Testing: New and/or updated tests have been added to cover my changes (if applicable).
• Documentation Impact: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Screenshots / Videos

Screenshots pending - this is a draft PR for early feedback.

Documentation Updates

• No documentation updates are required.

Additional Notes

This PR is an attempt to address Issue #10992. Feedback and guidance are welcome!

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Review complete. No issues found.

The implementation correctly:

• Reuses the existing importSettings message handler
• Uses the existing welcome:importSettings translation key
• Follows established patterns and styling conventions
• Maintains proper visual hierarchy

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