Reduce bcrypt cost

The default cost of 12 takes too long to execute. Reduce to 10, the same
as the default cost in Go.

With a cost of 12, login takes anywhere from 200 - 500ms to execute on a
Ryzen 7 3800X in release, and up to 4s in debug. In comparison, a cost
of 10 takes 50ms in release and 200ms in debug.

backend-rs/src/models/user.rs

@@ -71,7 +71,7 @@ pub async fn create(
 ) -> Result<User, CreateError> {
   let id = snowflakes.user_snowflake.lock().await.get_id();
   let time = Local::now().fixed_offset();
-  let hashed_pasword = bcrypt::hash(user.password, bcrypt::DEFAULT_COST)?;
+  let hashed_pasword = bcrypt::hash(user.password, 10)?;
 
   Ok(
     ActiveModel {