Bux fix

Bug: when getting user by id, it would try to parse i16 to i32, type
changed

backend/migrations/20260422094717_user_table.sql

@@ -2,7 +2,10 @@ CREATE TABLE users (
     id SMALLINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
     last_name VARCHAR(30),
     first_name VARCHAR(30),
-    username VARCHAR(30),
+    username VARCHAR(30) UNIQUE,
     pwd TEXT,
     is_admin BOOLEAN NOT NULL DEFAULT false
 );
+
+INSERT INTO users(last_name, first_name, username, pwd, is_admin) VALUES ('Raffauf', 'Silas', 'raffaufsil', 
+    '$argon2id$v=19$m=19456,t=2,p=1$urV91vY49mehWQoShkm6pw$1AGLuMDuFnY1CKuQU9ed89s1u9kvuszQjX+eIXmCBKI', true);

backend/src/handlers/auth.rs

@@ -220,7 +220,7 @@ pub async fn get_users(
 }
 
 pub async fn get_user_by_id(
-    Path(id): Path<i32>,
+    Path(id): Path<i16>,
     State(data): State<Arc<AppState>>,
 ) -> Result<impl IntoResponse, (StatusCode, Json<serde_json::Value>)> {
     let query = sqlx::query_as::<_, User>(r#"SELECT * FROM users WHERE id = $1"#)