perf: suspend hidden Windows webviews (#1972)

* perf: suspend hidden Windows webviews

Keep Close to Tray and the pre-created tray flyout alive while using WebView2 suspension to reclaim hidden UI memory. Resume before show and retain only the latest hidden flyout frame so App-to-WebView events cannot wake it implicitly.\n\nRecord the Windows lifecycle decision in ADR 0017 and the controller visibility invariant discovered during real-hardware validation.\n\nRefs #1962

* perf: gate WebView logging imports to Windows

Keep the Windows-only logging macros out of non-Windows builds so the cross-platform Tauri lint matrix remains warning-free.

* perf: cover all hidden WebView transitions