feat: add is_admin to User, count_users, ProviderConfigRepository trait, admin migration

k-tv-backend/infra/src/user_repository/mapping.rs

@@ -10,6 +10,7 @@ pub(super) struct UserRow {
     pub subject: String,
     pub email: String,
     pub password_hash: Option<String>,
+    pub is_admin: i64,
     pub created_at: String,
 }
 
@@ -36,6 +37,7 @@ impl TryFrom<UserRow> for User {
             row.subject,
             email,
             row.password_hash,
+            row.is_admin != 0,
             created_at,
         ))
     }