feat: [US-044] - Project sharing and collaborator management

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

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

@@ -20,15 +20,43 @@ export default async function EditorPage({ params }: PageProps) {
     return null
   }
 
-  const { data: project, error } = await supabase
+  // Try to load as owner first
+  const { data: ownedProject } = await supabase
     .from('projects')
     .select('id, name, flowchart_data')
     .eq('id', projectId)
     .eq('user_id', user.id)
     .single()
 
-  if (error || !project) {
-    notFound()
+  let project = ownedProject
+  let isOwner = true
+
+  // If not the owner, check if the user is a collaborator
+  if (!project) {
+    // RLS on projects allows collaborators to SELECT shared projects
+    const { data: collab } = await supabase
+      .from('project_collaborators')
+      .select('id, role')
+      .eq('project_id', projectId)
+      .eq('user_id', user.id)
+      .single()
+
+    if (!collab) {
+      notFound()
+    }
+
+    const { data: sharedProject } = await supabase
+      .from('projects')
+      .select('id, name, flowchart_data')
+      .eq('id', projectId)
+      .single()
+
+    if (!sharedProject) {
+      notFound()
+    }
+
+    project = sharedProject
+    isOwner = false
   }
 
   const rawData = project.flowchart_data || {}
@@ -74,6 +102,7 @@ export default async function EditorPage({ params }: PageProps) {
         <FlowchartEditor
           projectId={project.id}
           userId={user.id}
+          isOwner={isOwner}
           initialData={flowchartData}
           needsMigration={needsMigration}
         />