feat(ui): make dialogs theme aware

[CalvinAllen]

Description

The extension dialogs (rename dialog and progress dialog) should be theme aware and respond to Visual Studio's light/dark theme settings.

Current Behavior

Dialogs use fixed colors that may not match the user's VS theme.

Expected Behavior

Dialogs should automatically adapt their colors (background, text, borders, etc.) to match the current Visual Studio theme (Light, Dark, Blue, etc.).

Acceptance Criteria

• Rename dialog respects VS theme colors
• Progress dialog respects VS theme colors
• Dialogs are readable in both light and dark themes