feat: add Settlements, SMS, User detail, and Users management pages

- Implement SettlementsPage for managing settlement requests with approval and rejection functionalities.
- Create SmsPage for handling SMS templates, including creation, approval, rejection, and logging.
- Add UserDetailPage to display detailed information about users.
- Develop UsersPage for listing users with search, view, edit, and delete options.
- Introduce new types for User, SmsTemplate, SmsLog, and Settlement to support the new features.

assets/admin/components/ui/PageHeader.tsx

@@ -0,0 +1,40 @@
+import React from 'react';
+import { Link } from 'react-router-dom';
+
+interface Crumb {
+  label: string;
+  to?: string;
+}
+
+interface Props {
+  title: string;
+  breadcrumbs?: Crumb[];
+  action?: React.ReactNode;
+}
+
+export default function PageHeader({ title, breadcrumbs, action }: Props) {
+  return (
+    <div className="flex items-start justify-between mb-6">
+      <div>
+        <h1 className="text-xl font-bold text-gray-900">{title}</h1>
+        {breadcrumbs && breadcrumbs.length > 0 && (
+          <nav className="flex items-center gap-1 mt-1 text-sm text-gray-500">
+            {breadcrumbs.map((crumb, i) => (
+              <React.Fragment key={i}>
+                {i > 0 && <span className="text-gray-300">/</span>}
+                {crumb.to ? (
+                  <Link to={crumb.to} className="hover:text-primary-600 transition-colors">
+                    {crumb.label}
+                  </Link>
+                ) : (
+                  <span className="text-gray-700">{crumb.label}</span>
+                )}
+              </React.Fragment>
+            ))}
+          </nav>
+        )}
+      </div>
+      {action && <div>{action}</div>}
+    </div>
+  );
+}