feat: Implement first admin setup guard to lock registration after initial account creation

- Updated the registration flow to check if the first admin account has been created, preventing further public registrations.
- Introduced `is_first_admin_setup_available` function to determine registration availability.
- Modified the `/register` and `/login` pages to redirect based on the setup state.
- Enhanced the user creation process to handle internal admin accounts correctly.
- Added migration script to enforce the new registration rules in the database.
- Refactored chat API to improve message handling and context building.
- Updated dashboard and settings components for better state management.
- Improved error handling and user feedback across various components.

app/(dashboard)/dashboard-client.tsx

@@ -123,7 +123,7 @@ export function DashboardClient({ data }: DashboardClientProps) {
             <Plus className="h-4 w-4" />
             Hızlı Ekle
           </Button>
-          <QuickActionsSheet open={isQuickActionOpen} onOpenChange={setIsQuickActionOpen} />
+          <QuickActionsSheet isOpen={isQuickActionOpen} onClose={() => setIsQuickActionOpen(false)} />
         </div>
       </div>