Add user management system with JWT authentication

- Database schema: users, permissions, client_access tables
- Auth: JWT tokens with Argon2 password hashing
- API: login, user CRUD, permission management
- Dashboard: login required, admin Users tab
- Auto-creates initial admin user on first run

server/src/db/mod.rs

@@ -7,6 +7,7 @@ pub mod machines;
 pub mod sessions;
 pub mod events;
 pub mod support_codes;
+pub mod users;
 
 use anyhow::Result;
 use sqlx::postgres::PgPoolOptions;
@@ -17,6 +18,7 @@ pub use machines::*;
 pub use sessions::*;
 pub use events::*;
 pub use support_codes::*;
+pub use users::*;
 
 /// Database connection pool wrapper
 #[derive(Clone)]