feat: [US-046] - Presence indicators for active collaborators

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/editor/[projectId]/page.tsx

@@ -20,6 +20,15 @@ export default async function EditorPage({ params }: PageProps) {
     return null
   }
 
+  // Fetch user's display name for presence
+  const { data: profile } = await supabase
+    .from('profiles')
+    .select('display_name')
+    .eq('id', user.id)
+    .single()
+
+  const userDisplayName = profile?.display_name || user.email || 'Anonymous'
+
   // Try to load as owner first
   const { data: ownedProject } = await supabase
     .from('projects')
@@ -102,6 +111,7 @@ export default async function EditorPage({ params }: PageProps) {
         <FlowchartEditor
           projectId={project.id}
           userId={user.id}
+          userDisplayName={userDisplayName}
           isOwner={isOwner}
           initialData={flowchartData}
           needsMigration={needsMigration}