docs: document more ways to secure the data api (#27756)

Document ways to increase the security of Data API, including:

- Disabling it entirely
- Exposing a custom schema instead of the `public` schema

Also found a duplicated link in the nav for CLS, so removed it.

apps/docs/components/Navigation/NavigationMenu/NavigationMenu.constants.ts

@@ -734,6 +734,10 @@ export const database: NavMenuConstant = {
           name: 'Column Level Security',
           url: '/guides/database/postgres/column-level-security',
         },
+        {
+          name: 'Hardening the Data API',
+          url: '/guides/database/hardening-data-api',
+        },
         {
           name: 'Custom Claims & RBAC',
           url: '/guides/database/postgres/custom-claims-and-role-based-access-control-rbac',
@@ -747,10 +751,6 @@ export const database: NavMenuConstant = {
           name: 'Superuser Access and Unsupported Operations',
           url: '/guides/database/postgres/roles-superuser',
         },
-        {
-          name: 'Column level privileges',
-          url: '/guides/database/postgres/column-level-security',
-        },
       ],
     },
     {