feat: toast notifications for key session events (clear, export, import, disconnect)

[Agboolafeyikemi]

🔗 Linked issue

Description

Adds themed, theme-aware toast notifications (via the already-installed react-hot-toast) for four high-signal user events in the Reactime panel. Today these actions mutate state silently users have to re-inspect the UI to verify the action actually worked, and a port disconnect can go unnoticed until the next interaction fails. These toasts give immediate, confidence-building feedback and, in the disconnect case, a one-click path to recovery.

Checklist

• [x ] I've followed the Contributing guidelines

• [x ] I've titled my PR according to the Conventional Commits spec

• I've linked an open issue

• I've added tests that fail without this PR but pass with it

• [ x] I've linted and tested my code

• I've updated documentation (if appropriate)

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