refactor(frontend): replace confirm() with modern confirmation modals

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.

frontend/src/pages/DashboardPage.jsx

@@ -7,6 +7,7 @@ import { dashboardAPI, matchesAPI } from '../services/api';
 import { connectSocket, disconnectSocket, getSocket } from '../services/socket';
 import { DashboardSkeleton } from '../components/common/Skeleton';
 import EmptyState from '../components/common/EmptyState';
+import ConfirmationModal from '../components/modals/ConfirmationModal';
 import {
   DashboardEventCard,
   DashboardMatchCard,
@@ -28,6 +29,9 @@ const DashboardPage = () => {
   const { user } = useAuth();
   const [data, setData] = useState(null);
   const [loading, setLoading] = useState(true);
+  const [showDeclineModal, setShowDeclineModal] = useState(false);
+  const [showCancelModal, setShowCancelModal] = useState(false);
+  const [matchToProcess, setMatchToProcess] = useState(null);
   const [error, setError] = useState('');
   const [processingMatchId, setProcessingMatchId] = useState(null);
 
@@ -105,12 +109,17 @@ const DashboardPage = () => {
     }
   };
 
-  const handleRejectMatch = async (matchSlug) => {
-    if (!confirm('Are you sure you want to decline this request?')) return;
+  const handleRejectMatch = (matchSlug) => {
+    setMatchToProcess(matchSlug);
+    setShowDeclineModal(true);
+  };
+
+  const confirmRejectMatch = async () => {
+    if (!matchToProcess) return;
 
     try {
-      setProcessingMatchId(matchSlug);
-      await matchesAPI.deleteMatch(matchSlug);
+      setProcessingMatchId(matchToProcess);
+      await matchesAPI.deleteMatch(matchToProcess);
       toast.success('Request declined.');
       await loadDashboard();
     } catch (err) {
@@ -118,15 +127,22 @@ const DashboardPage = () => {
       toast.error('Failed to decline request. Please try again.');
     } finally {
       setProcessingMatchId(null);
+      setShowDeclineModal(false);
+      setMatchToProcess(null);
     }
   };
 
-  const handleCancelRequest = async (matchSlug) => {
-    if (!confirm('Are you sure you want to cancel this request?')) return;
+  const handleCancelRequest = (matchSlug) => {
+    setMatchToProcess(matchSlug);
+    setShowCancelModal(true);
+  };
+
+  const confirmCancelRequest = async () => {
+    if (!matchToProcess) return;
 
     try {
-      setProcessingMatchId(matchSlug);
-      await matchesAPI.deleteMatch(matchSlug);
+      setProcessingMatchId(matchToProcess);
+      await matchesAPI.deleteMatch(matchToProcess);
       toast.success('Request cancelled.');
       await loadDashboard();
     } catch (err) {
@@ -134,6 +150,8 @@ const DashboardPage = () => {
       toast.error('Failed to cancel request. Please try again.');
     } finally {
       setProcessingMatchId(null);
+      setShowCancelModal(false);
+      setMatchToProcess(null);
     }
   };
 
@@ -316,6 +334,38 @@ const DashboardPage = () => {
           </section>
         )}
       </div>
+
+      {/* Decline Confirmation Modal */}
+      <ConfirmationModal
+        isOpen={showDeclineModal}
+        onClose={() => {
+          setShowDeclineModal(false);
+          setMatchToProcess(null);
+        }}
+        onConfirm={confirmRejectMatch}
+        title="Decline Match Request"
+        message="Are you sure you want to decline this request? This action cannot be undone."
+        confirmText="Decline"
+        cancelText="Cancel"
+        isLoading={processingMatchId === matchToProcess}
+        loadingText="Declining..."
+      />
+
+      {/* Cancel Confirmation Modal */}
+      <ConfirmationModal
+        isOpen={showCancelModal}
+        onClose={() => {
+          setShowCancelModal(false);
+          setMatchToProcess(null);
+        }}
+        onConfirm={confirmCancelRequest}
+        title="Cancel Match Request"
+        message="Are you sure you want to cancel this request? This action cannot be undone."
+        confirmText="Cancel Request"
+        cancelText="Keep Request"
+        isLoading={processingMatchId === matchToProcess}
+        loadingText="Cancelling..."
+      />
     </Layout>
   );
 };