feat(dashboard): add unread count for match chats

Track unread messages in match chats and display count badge:
- Schema: Add user1LastReadAt/user2LastReadAt to Match model
- Backend: Calculate unreadCount in dashboard API
- Socket: Update lastReadAt when user joins match room
- Frontend: Display red badge with unread count on match avatar

backend/prisma/migrations/20251121204228_add_match_last_read_timestamps/migration.sql

@@ -0,0 +1,4 @@
+-- AlterTable
+ALTER TABLE "matches" ADD COLUMN     "user1_last_read_at" TIMESTAMP(3),
+ADD COLUMN     "user2_last_read_at" TIMESTAMP(3),
+ALTER COLUMN "slug" DROP DEFAULT;

backend/prisma/schema.prisma

@@ -134,14 +134,16 @@ model Message {
 
 // Matches (pairs of users for collaboration)
 model Match {
-  id        Int       @id @default(autoincrement())
-  slug      String    @unique @default(cuid()) @db.VarChar(50)
-  user1Id   Int       @map("user1_id")
-  user2Id   Int       @map("user2_id")
-  eventId   Int       @map("event_id")
-  roomId    Int?      @map("room_id")
-  status    String    @default("pending") @db.VarChar(20) // 'pending', 'accepted', 'completed'
-  createdAt DateTime  @default(now()) @map("created_at")
+  id              Int       @id @default(autoincrement())
+  slug            String    @unique @default(cuid()) @db.VarChar(50)
+  user1Id         Int       @map("user1_id")
+  user2Id         Int       @map("user2_id")
+  eventId         Int       @map("event_id")
+  roomId          Int?      @map("room_id")
+  status          String    @default("pending") @db.VarChar(20) // 'pending', 'accepted', 'completed'
+  createdAt       DateTime  @default(now()) @map("created_at")
+  user1LastReadAt DateTime? @map("user1_last_read_at")
+  user2LastReadAt DateTime? @map("user2_last_read_at")
 
   // Relations
   user1     User      @relation("MatchUser1", fields: [user1Id], references: [id])

backend/src/routes/dashboard.js

@@ -180,6 +180,14 @@ router.get('/', authenticate, async (req, res, next) => {
       const lastMessage = match.room?.messages[0];
       const lastMessageAt = lastMessage ? lastMessage.createdAt : match.createdAt;
 
+      // Calculate unread count
+      const myLastReadAt = isUser1 ? match.user1LastReadAt : match.user2LastReadAt;
+      const unreadCount = myLastReadAt
+        ? (match.room?.messages || []).filter(
+            (m) => m.userId !== userId && new Date(m.createdAt) > new Date(myLastReadAt)
+          ).length
+        : (match.room?.messages || []).filter((m) => m.userId !== userId).length;
+
       return {
         id: match.id,
         slug: match.slug,
@@ -197,6 +205,7 @@ router.get('/', authenticate, async (req, res, next) => {
         },
         videoExchange,
         ratings,
+        unreadCount,
         lastMessageAt,
         status: match.status,
       };

backend/src/socket/index.js

@@ -268,11 +268,35 @@ function initializeSocket(httpServer) {
     });
 
     // Join private match room
-    socket.on('join_match_room', ({ matchId }) => {
-      const roomName = `match_${matchId}`;
-      socket.join(roomName);
-      socket.currentMatchRoom = roomName;
-      console.log(`👥 ${socket.user.username} joined match room ${matchId}`);
+    socket.on('join_match_room', async ({ matchId }) => {
+      try {
+        const roomName = `match_${matchId}`;
+        socket.join(roomName);
+        socket.currentMatchRoom = roomName;
+        socket.currentMatchId = parseInt(matchId);
+        console.log(`👥 ${socket.user.username} joined match room ${matchId}`);
+
+        // Mark messages as read by updating lastReadAt
+        const match = await prisma.match.findUnique({
+          where: { id: parseInt(matchId) },
+          select: { user1Id: true, user2Id: true },
+        });
+
+        if (match) {
+          const isUser1 = match.user1Id === socket.user.id;
+          const updateData = isUser1
+            ? { user1LastReadAt: new Date() }
+            : { user2LastReadAt: new Date() };
+
+          await prisma.match.update({
+            where: { id: parseInt(matchId) },
+            data: updateData,
+          });
+        }
+      } catch (error) {
+        console.error('Join match room error:', error);
+        socket.emit('error', { message: 'Failed to join match room' });
+      }
     });
 
     // Send message to match room

frontend/src/pages/DashboardPage.jsx

@@ -356,7 +356,7 @@ const EventCard = ({ event }) => {
 // Match Card Component
 const MatchCard = ({ match }) => {
   const navigate = useNavigate();
-  const { partner, event, videoExchange, ratings } = match;
+  const { partner, event, videoExchange, ratings, unreadCount } = match;
 
   // Can rate when video exchange is complete and user hasn't rated yet
   const canRate = videoExchange?.sentByMe && videoExchange?.receivedFromPartner && !ratings?.ratedByMe;
@@ -365,12 +365,17 @@ const MatchCard = ({ match }) => {
     <div className="bg-white rounded-lg shadow-sm border border-gray-200 p-4 hover:shadow-md transition-shadow">
       <div className="flex items-start gap-4">
         {/* Avatar */}
-        <Link to={`/${partner.username}`} className="flex-shrink-0">
+        <Link to={`/${partner.username}`} className="flex-shrink-0 relative">
           <img
             src={partner.avatar || `https://api.dicebear.com/7.x/avataaars/svg?seed=${partner.username}`}
             alt={partner.username}
             className="w-12 h-12 rounded-full hover:ring-2 hover:ring-primary-500 transition-all"
           />
+          {unreadCount > 0 && (
+            <span className="absolute -top-1 -right-1 bg-red-500 text-white text-xs rounded-full h-5 w-5 flex items-center justify-center font-semibold">
+              {unreadCount > 9 ? '9+' : unreadCount}
+            </span>
+          )}
         </Link>
 
         {/* Content */}

frontend/src/pages/__tests__/DashboardPage.test.jsx

@@ -507,6 +507,68 @@ describe('DashboardPage', () => {
     });
   });
 
+  describe('Unread Count Display', () => {
+    it('should display unread count badge when there are unread messages', async () => {
+      dashboardAPI.getData.mockResolvedValue({
+        activeEvents: [],
+        activeMatches: [
+          {
+            id: 1,
+            slug: 'match-123',
+            partner: {
+              id: 2,
+              username: 'sarah_dancer',
+              firstName: 'Sarah',
+              lastName: 'Martinez',
+              avatar: null,
+            },
+            event: { id: 1, name: 'Test Event' },
+            videoExchange: { sentByMe: false, receivedFromPartner: false },
+            ratings: { ratedByMe: false, ratedByPartner: false },
+            unreadCount: 5,
+          },
+        ],
+        matchRequests: { incoming: [], outgoing: [] },
+      });
+
+      renderWithRouter(<DashboardPage />);
+
+      await waitFor(() => {
+        expect(screen.getByText('5')).toBeInTheDocument();
+      });
+    });
+
+    it('should show 9+ for more than 9 unread messages', async () => {
+      dashboardAPI.getData.mockResolvedValue({
+        activeEvents: [],
+        activeMatches: [
+          {
+            id: 1,
+            slug: 'match-123',
+            partner: {
+              id: 2,
+              username: 'sarah_dancer',
+              firstName: 'Sarah',
+              lastName: 'Martinez',
+              avatar: null,
+            },
+            event: { id: 1, name: 'Test Event' },
+            videoExchange: { sentByMe: false, receivedFromPartner: false },
+            ratings: { ratedByMe: false, ratedByPartner: false },
+            unreadCount: 15,
+          },
+        ],
+        matchRequests: { incoming: [], outgoing: [] },
+      });
+
+      renderWithRouter(<DashboardPage />);
+
+      await waitFor(() => {
+        expect(screen.getByText('9+')).toBeInTheDocument();
+      });
+    });
+  });
+
   describe('Rating Status Display', () => {
     it('should show rating status indicators', async () => {
       dashboardAPI.getData.mockResolvedValue({