fix: downgrade rand_core to 0.6 for argon2 compatibility

rand_core 0.9.x changed OsRng API (no longer implements RngCore directly)
and is incompatible with argon2 0.5.x which depends on rand_core 0.6.x.
This caused compilation failures in CI.

Author: Dionisio

Cargo.lock

@@ -32,7 +32,7 @@ sqlx = { version = "0.8.6", features = ["postgres", "runtime-tokio", "tls-rustls
 anyhow = "1.0.101"
 jsonwebtoken = { version = "10.1.0", features = ["rust_crypto"] }
 argon2 = "0.5.3"
-rand_core = { version = "0.9.5", features = ["std"] }
+rand_core = { version = "0.6", features = ["std", "getrandom"] }
 hyper = { version = "1.8.1", features = ["full"] }
 quick-xml = "0.39.0"
 dotenv = "0.15.0"