Improve staff management UI and add sorting functionality

- Remove WIP badge from staff sidebar navigation
- Make action buttons consistent between Customers and Staff pages
  - Edit button: icon + text with gray border
  - Masquerade button: icon + text with indigo border
  - Verify email button: icon-only with colored border (green/amber)
- Add sortable columns to Staff list (name and role)
- Include migrations for tenant manager role removal

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/components/__tests__/MasqueradeBanner.test.tsx

@@ -50,7 +50,7 @@ describe('MasqueradeBanner', () => {
   it('shows return to previous user text when previousUser exists', () => {
     const propsWithPrevious = {
       ...defaultProps,
-      previousUser: { id: '3', name: 'Manager', email: 'manager@test.com', role: 'manager' as const },
+      previousUser: { id: '3', name: 'Manager', email: 'manager@test.com', role: 'owner' as const },
     };
     render(<MasqueradeBanner {...propsWithPrevious} />);
     expect(screen.getByText(/platform.masquerade.returnTo/)).toBeInTheDocument();

frontend/src/components/__tests__/TopBar.test.tsx

@@ -518,8 +518,8 @@ describe('TopBar', () => {
       expect(screen.getByTestId('user-profile-dropdown')).toBeInTheDocument();
     });
 
-    it('should render for manager role', () => {
-      const user = createMockUser({ role: 'manager' });
+    it('should render for staff with permissions', () => {
+      const user = createMockUser({ role: 'staff' });
 
       renderWithRouter(
         <TopBar