fix: paginate listRoles, null-guard permissions handler, fix export ordering

- Add limit/offset/total pagination to listRoles matching the groups pattern
- Add countRoles data-layer method
- Omit permissions from listRoles select (getRole returns full document)
- Null-guard re-fetched role in updateRolePermissionsHandler
- Move interleaved export below all imports in methods/index.ts

api/server/routes/admin/roles.js

@@ -13,6 +13,7 @@ const requireManageRoles = requireCapability(SystemCapabilities.MANAGE_ROLES);
 
 const handlers = createAdminRolesHandlers({
   listRoles: db.listRoles,
+  countRoles: db.countRoles,
   getRoleByName: db.getRoleByName,
   createRoleByName: db.createRoleByName,
   updateRoleByName: db.updateRoleByName,