feat: add public user profiles

- Add GET /api/users/:username endpoint for public profiles
- Create PublicProfilePage component with user stats and info
- Add getUserByUsername function to API service
- Add /:username route to App.jsx
- Display user info: name, location, stats, WSDC ID, social links
- Only show public data (no email or sensitive information)
- Accessible only to authenticated users

Users can now view public profiles of other users by visiting
/<username>. The profile displays stats, location, WSDC ID, and
social media links.

backend/src/routes/users.js

@@ -81,4 +81,71 @@ router.patch('/me', authenticate, updateProfileValidation, updateProfile);
 // PATCH /api/users/me/password - Change password
 router.patch('/me/password', authenticate, changePasswordValidation, changePassword);
 
+// GET /api/users/:username - Get public user profile by username
+router.get('/:username', authenticate, async (req, res, next) => {
+  try {
+    const { username } = req.params;
+
+    const user = await prisma.user.findUnique({
+      where: { username },
+      select: {
+        id: true,
+        username: true,
+        firstName: true,
+        lastName: true,
+        wsdcId: true,
+        youtubeUrl: true,
+        instagramUrl: true,
+        facebookUrl: true,
+        tiktokUrl: true,
+        country: true,
+        city: true,
+        avatar: true,
+        createdAt: true,
+        _count: {
+          select: {
+            matchesAsUser1: true,
+            matchesAsUser2: true,
+            ratingsReceived: true,
+          },
+        },
+      },
+    });
+
+    if (!user) {
+      return res.status(404).json({
+        success: false,
+        error: 'User not found',
+      });
+    }
+
+    // Calculate total matches
+    const totalMatches = user._count.matchesAsUser1 + user._count.matchesAsUser2;
+
+    // Calculate average rating
+    const ratings = await prisma.rating.findMany({
+      where: { ratedId: user.id },
+      select: { score: true },
+    });
+
+    const averageRating = ratings.length > 0
+      ? ratings.reduce((sum, r) => sum + r.score, 0) / ratings.length
+      : 0;
+
+    res.json({
+      success: true,
+      data: {
+        ...user,
+        stats: {
+          matchesCount: totalMatches,
+          ratingsCount: user._count.ratingsReceived,
+          rating: averageRating.toFixed(1),
+        },
+      },
+    });
+  } catch (error) {
+    next(error);
+  }
+});
+
 module.exports = router;