added tower_governor crate, added some basic rate limiting

backend/public/Cargo.toml

@@ -9,6 +9,7 @@ authors = ["Wyatt J. Miller <wyatt@wyattjmiller.com"]
 [dependencies]
 axum = "0.7.6"
 tower-http = { version = "0.6.1", features = ["trace"] }
+tower_governor = "0.4.2"
 tokio = { version = "1.40.0", features = ["full"] }
 sqlx = { version = "0.8.2", features = [
   "runtime-tokio-rustls",