refactor: remove screenshot functionality and headless_chrome dependency

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.

src/lib/api.ts

@@ -1481,38 +1481,7 @@ export const api = {
     }
   },
 
-  /**
-   * Captures a screenshot of a specific region in the window
-   * @param url - The URL to capture
-   * @param selector - Optional selector to capture
-   * @param fullPage - Whether to capture the full page
-   * @returns Promise resolving to the path of the saved screenshot
-   */
-  async captureUrlScreenshot(
-    url: string,
-    selector?: string | null,
-    fullPage: boolean = false
-  ): Promise<string> {
-    return await invoke<string>("capture_url_screenshot", {
-      url,
-      selector,
-      fullPage,
-    });
-  },
 
-  /**
-   * Cleans up old screenshot files from the temporary directory
-   * @param olderThanMinutes - Remove files older than this many minutes (default: 60)
-   * @returns Promise resolving to the number of files deleted
-   */
-  async cleanupScreenshotTempFiles(olderThanMinutes?: number): Promise<number> {
-    try {
-      return await invoke<number>("cleanup_screenshot_temp_files", { olderThanMinutes });
-    } catch (error) {
-      console.error("Failed to cleanup screenshot files:", error);
-      throw error;
-    }
-  },
 
   /**
    * List all available Claude installations on the system