refactor: rename Alice to Nina across test and seed scripts

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/admin/users_test.go

@@ -35,7 +35,7 @@ func TestAdminUsers_List(t *testing.T) {
 	_, err := db.DB.Exec(context.Background(), `
 		INSERT INTO users (n_first_name, n_last_name, email, phone, date_of_birth, password_hash, account_role, account_type)
 		VALUES
-			('Alice', 'Smith', 'alice@test.com', '+447123456789', '1990-01-01', 'hash1', 'admin', 'email'),
+			('Nina', 'Smith', 'nina@test.com', '+447123456789', '1990-01-01', 'hash1', 'admin', 'email'),
 			('Bob', 'Jones', 'bob@test.com', '+447123456789', '1990-01-01', 'hash2', 'verified_email', 'email'),
 			('Charlie', 'Brown', 'charlie@test.com', '+447123456789', '1990-01-01', 'hash3', 'verified_email', 'email')
 	`)