Remove the screenshot capture system and associated UI components to simplify the codebase.
- Remove screenshot.rs command module and related functionality
- Remove headless_chrome dependency from Cargo.toml
- Update Cargo.lock to reflect dependency changes
- Remove screenshot handlers and UI from WebviewPreview component
- Clean up screenshot-related API calls and imports
- Remove camera icon and capture controls from preview interface
This reduces bundle size and eliminates an underutilized feature.