Replaced all confirm() dialogs with reusable ConfirmationModal component
for better UX. Modal dialogs provide clearer context, visual consistency,
and prevent accidental confirmations.
Changes:
- MatchesPage: Reject match request confirmation modal
- DashboardPage: Decline and cancel request confirmation modals
- ContactMessagesPage: Delete message confirmation modal
All modals support loading states during async operations and provide
clear action descriptions with destructive action styling.
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