feat: pre-populate heats form with existing data when editing

- Add existingHeats prop to HeatsBanner component
- Load and format existing heats into form fields
- Pass myHeats to HeatsBanner in edit modal
- Users can now edit their heats instead of starting from scratch

frontend/src/components/heats/HeatsBanner.jsx

@@ -2,7 +2,7 @@ import { useState, useEffect } from 'react';
 import { X, Plus, Trash2, Loader2 } from 'lucide-react';
 import { divisionsAPI, competitionTypesAPI, heatsAPI } from '../../services/api';
 
-export default function HeatsBanner({ slug, onSave, onDismiss }) {
+export default function HeatsBanner({ slug, onSave, onDismiss, existingHeats = null }) {
   const [divisions, setDivisions] = useState([]);
   const [competitionTypes, setCompetitionTypes] = useState([]);
   const [heats, setHeats] = useState([{ divisionId: '', competitionTypeId: '', heatNumber: '', role: '' }]);
@@ -14,6 +14,19 @@ export default function HeatsBanner({ slug, onSave, onDismiss }) {
     loadOptions();
   }, []);
 
+  // Load existing heats if provided
+  useEffect(() => {
+    if (existingHeats && existingHeats.length > 0) {
+      const formattedHeats = existingHeats.map(heat => ({
+        divisionId: heat.divisionId.toString(),
+        competitionTypeId: heat.competitionTypeId.toString(),
+        heatNumber: heat.heatNumber.toString(),
+        role: heat.role || '',
+      }));
+      setHeats(formattedHeats);
+    }
+  }, [existingHeats]);
+
   const loadOptions = async () => {
     try {
       setLoading(true);

frontend/src/pages/EventChatPage.jsx

@@ -717,6 +717,7 @@ const EventChatPage = () => {
                   slug={slug}
                   onSave={handleHeatsSave}
                   onDismiss={() => setShowHeatsModal(false)}
+                  existingHeats={myHeats}
                 />
               </div>
             </div>