feat: track event participation and show joined events first

Backend:
- Add EventParticipant model to track user-event participation
- Create database migration for event_participants table
- Record participation when user joins event chat via Socket.IO
- Update GET /api/events to include isJoined flag for current user
- Sort events: joined events first, then by start date
- Add authenticate middleware to GET /api/events

Frontend:
- Replace mock events with real API data from backend
- Add loading and error states to EventsPage
- Display "Joined" badge on events user has joined
- Highlight joined events with colored border
- Show "Open chat" vs "Join chat" button text
- Auto-refresh events list when navigating back

When users join an event chat, this is now recorded in the database.
Joined events appear at the top of the list with visual indicators.

frontend/src/pages/EventsPage.jsx

@@ -1,15 +1,61 @@
+import { useState, useEffect } from 'react';
 import { useNavigate } from 'react-router-dom';
 import Layout from '../components/layout/Layout';
-import { mockEvents } from '../mocks/events';
-import { Calendar, MapPin, Users } from 'lucide-react';
+import { eventsAPI } from '../services/api';
+import { Calendar, MapPin, Users, Loader2, CheckCircle } from 'lucide-react';
 
 const EventsPage = () => {
   const navigate = useNavigate();
+  const [events, setEvents] = useState([]);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState('');
+
+  useEffect(() => {
+    const fetchEvents = async () => {
+      try {
+        setLoading(true);
+        const data = await eventsAPI.getAll();
+        setEvents(data);
+      } catch (err) {
+        setError('Failed to load events');
+        console.error('Error loading events:', err);
+      } finally {
+        setLoading(false);
+      }
+    };
+
+    fetchEvents();
+  }, []);
 
   const handleJoinEvent = (eventId) => {
     navigate(`/events/${eventId}/chat`);
   };
 
+  if (loading) {
+    return (
+      <Layout>
+        <div className="max-w-4xl mx-auto flex items-center justify-center min-h-[400px]">
+          <div className="flex flex-col items-center gap-3">
+            <Loader2 className="w-12 h-12 animate-spin text-primary-600" />
+            <p className="text-gray-600">Loading events...</p>
+          </div>
+        </div>
+      </Layout>
+    );
+  }
+
+  if (error) {
+    return (
+      <Layout>
+        <div className="max-w-4xl mx-auto">
+          <div className="bg-red-50 border border-red-200 rounded-md p-4 text-red-700">
+            {error}
+          </div>
+        </div>
+      </Layout>
+    );
+  }
+
   return (
     <Layout>
       <div className="max-w-4xl mx-auto">
@@ -17,12 +63,22 @@ const EventsPage = () => {
         <p className="text-gray-600 mb-8">Join an event and start connecting with other dancers</p>
 
         <div className="grid gap-6 md:grid-cols-2">
-          {mockEvents.map((event) => (
+          {events.map((event) => (
             <div
               key={event.id}
-              className="bg-white rounded-lg shadow-md hover:shadow-lg transition-shadow p-6 border border-gray-200"
+              className={`bg-white rounded-lg shadow-md hover:shadow-lg transition-shadow p-6 border-2 ${
+                event.isJoined ? 'border-primary-500' : 'border-gray-200'
+              }`}
             >
-              <h3 className="text-xl font-bold text-gray-900 mb-3">{event.name}</h3>
+              <div className="flex items-start justify-between mb-3">
+                <h3 className="text-xl font-bold text-gray-900">{event.name}</h3>
+                {event.isJoined && (
+                  <span className="flex items-center gap-1 px-2 py-1 bg-primary-100 text-primary-700 text-xs font-medium rounded-full">
+                    <CheckCircle className="w-3 h-3" />
+                    Joined
+                  </span>
+                )}
+              </div>
 
               <div className="space-y-2 mb-4">
                 <div className="flex items-center text-gray-600">
@@ -32,22 +88,24 @@ const EventsPage = () => {
                 <div className="flex items-center text-gray-600">
                   <Calendar className="w-4 h-4 mr-2" />
                   <span className="text-sm">
-                    {new Date(event.start_date).toLocaleDateString('en-US')} - {new Date(event.end_date).toLocaleDateString('en-US')}
+                    {new Date(event.startDate).toLocaleDateString('en-US')} - {new Date(event.endDate).toLocaleDateString('en-US')}
                   </span>
                 </div>
                 <div className="flex items-center text-gray-600">
                   <Users className="w-4 h-4 mr-2" />
-                  <span className="text-sm">{event.participants_count} participants</span>
+                  <span className="text-sm">{event.participantsCount} participants</span>
                 </div>
               </div>
 
-              <p className="text-gray-600 text-sm mb-4">{event.description}</p>
+              {event.description && (
+                <p className="text-gray-600 text-sm mb-4">{event.description}</p>
+              )}
 
               <button
                 onClick={() => handleJoinEvent(event.id)}
                 className="w-full px-4 py-2 bg-primary-600 text-white rounded-md hover:bg-primary-700 transition-colors"
               >
-                Join chat
+                {event.isJoined ? 'Open chat' : 'Join chat'}
               </button>
             </div>
           ))}