Fix user schema to match database structure

Updated backend to use single 'name' field instead of 'first_name' and 'last_name'
to match the actual database schema where users table has a 'name' column.

Changes:
- Updated User and UserPublic interfaces to use 'name' and 'avatar_url'
- Updated user validators to use 'name' instead of first/last names
- Updated all SQL queries in user.service.ts to select u.name
- Updated search filters and sort columns
- Fixed user creation and update operations

This resolves the "column u.first_name does not exist" error.

water-api/src/controllers/user.controller.ts

@@ -128,8 +128,8 @@ export async function createUser(
     const user = await userService.create({
       email: data.email,
       password: data.password,
-      first_name: data.first_name,
-      last_name: data.last_name,
+      name: data.name,
+      avatar_url: data.avatar_url,
       role_id: data.role_id,
       is_active: data.is_active,
     });