* fix(shutdown): mark shutdown as exiting to stop background tasks
- lib.rs:570 → Flag app as exiting on ExitRequested, notify proxy guard, start cleanup immediately, with fallback in Exit event
- tray/mod.rs:190 → Add unified exit checks around tray init/updates to prevent UI recreation during shutdown
- event_driven_proxy.rs:252 → Ensure proxy guard skips all restore/re-enable work (including sysproxy.exe calls) once exit flag is set
* fix(shutdown): refine exit handling and proxy guard notifications
* fix(shutdown): add guard to run shutdown routine only once per lifecycle
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