feat: Add automatic token refresh for Claude Code authentication

[roomote]

This PR implements automatic background token refresh for Claude Code authentication, eliminating the need for users to continuously re-approve authentication via browser.

Changes

• Background Token Refresh: Implements automatic token refresh using RefreshTimer that runs every 50 minutes (before the 60-minute token expiry)
• Proactive Refresh: Tokens are refreshed proactively before they expire, ensuring uninterrupted service
• Exponential Backoff: Added retry logic with exponential backoff (max 3 attempts) for failed refresh operations
• User Notifications: Displays a clear notification when re-authentication is required after max retry attempts
• Lifecycle Management: Properly handles initialization and cleanup (dispose) of the refresh timer
• Package Export: Exported RefreshTimer from @roo-code/cloud package for reuse

Testing

• Added comprehensive unit tests for token refresh functionality
• All existing tests continue to pass
• Tested initialization, refresh success, refresh failure, and retry logic scenarios

Technical Details

The implementation follows the same pattern as WebAuthService in the cloud package, ensuring consistency across authentication services.

Token Lifecycle:

1. On initialization, if credentials exist, start the refresh timer
2. Timer checks every 50 minutes if token is within 10 minutes of expiry
3. If near expiry, refreshes the token automatically in the background
4. On refresh failure, increments attempt counter (max 3 attempts)
5. After max attempts, clears credentials and notifies user to re-authenticate

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[roomote]

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Review complete. Found 1 issue:

• "Sign In" button in re-authentication notification does nothing when clicked (oauth.ts:607-611)

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[roomote]

The "Sign In" button does nothing when clicked - it only logs a message. The comment says "This will be handled by the UI layer" but there's no mechanism to communicate the user's action to the UI. Users who click "Sign In" expecting to authenticate will see nothing happen, which is a confusing UX. Consider either triggering the OAuth flow via a VS Code command (e.g., vscode.commands.executeCommand('roo-cline.claudeCodeOAuthLogin')) or removing the "Sign In" button if the action cannot be implemented in this layer.

_{Fix it with Roo Code or mention @roomote and request a fix.}