Testing: Add Windows UI automation tests (FlaUI) #23

Issue Description

Add Windows desktop UI automation tests for xBeacon using the existing .NET/xUnit stack. This enables local, repeatable validation of WPF/WinForms UI flows (dashboard, tray interactions, status indicators) without manual testing.

Why FlaUI (vs WinAppDriver)

• No external service: FlaUI is a pure .NET library; WinAppDriver requires installing and running a separate driver service.
• Simpler local dev loop: tests can run with dotnet test without extra setup.
• Great fit for WPF/WinForms: FlaUI UIA3 works well for desktop UI automation in .NET apps.
• Lower maintenance: fewer moving parts in CI and for contributors.

When WinAppDriver still makes sense

• You already use Appium/WebDriver elsewhere.
• You need WebDriver tooling or cross‑language test clients.
• You want to standardize on a single driver protocol.

Proposed Implementation Plan

1. Create a new test project tests/xBeacon.Tests.UI targeting net8.0-windows with xUnit.
2. Add FlaUI packages (FlaUI.Core, FlaUI.UIA3) and a helper to launch/attach to xBeacon.Windows.
3. Add smoke UI tests:
   • App launches and dashboard opens (either via test flag or direct window handle).
   • Status indicator renders expected state.
   • Basic notifications list renders without error.
4. Add a --ui-test flag or test config to run app in deterministic mode.
5. Document local test steps and note CI requirement (self‑hosted Windows runner with desktop session).

Acceptance Criteria

• At least 2–3 UI smoke tests pass locally on Windows 11.
• Tests can launch and close xBeacon cleanly without leaving processes.
• Docs explain how to run UI tests locally.

Files/Areas Likely Affected

• New test project under tests/
• src/xBeacon.Windows (optional test mode flag)
• Documentation updates for running UI tests

Notes

• Current test framework is xUnit (tests/WinBeacon.Tests.Unit/WinBeacon.Tests.Unit.csproj).
• WinAppDriver remains a viable alternative if we need WebDriver tooling later.