Quant.Infra.Net.Pro.Web.CharleSchwabIntegration

Fix: Cross-platform interactive authorization—replaced the system browser with Playwright to resolve Firefox/dconf authorization failures under Linux sudo.

Key changes:

• Added SchwabInteractiveAuthService: Uses Playwright Chromium (visible window) to complete the initial OAuth authorization, eliminating reliance on the system browser.
• Added a "Quick Authorize" button to the Sign-In page.
• Program.cs: Skipped automatic browser launching via Process.Start on Linux (to avoid sudo + snap dconf issues).
• SignInController fixes: Changed "fire-and-forget" Task.Run to await; changed HttpContext.RequestAborted to CancellationToken.None.
• Added status banners to the Dashboard for "Unauthorized" and "Authorization Expiring Soon" states.