Implement tick-based game loop, combat overhaul, and attack-any-NPC

Replace immediate combat with a 3-second tick engine that resolves
actions, NPC AI, status effects, respawns, and passive regeneration.
Players queue combat actions (attack/defend/flee/use) that resolve on
the next tick. Any NPC can now be attacked — non-hostile targets incur
attitude penalties instead of being blocked. Status effects persist in
the database and continue ticking while players are offline.

Made-with: Cursor

src/main.rs

@@ -9,6 +9,7 @@ use tokio::net::TcpListener;
 use mudserver::db;
 use mudserver::game;
 use mudserver::ssh;
+use mudserver::tick;
 use mudserver::world;
 
 const DEFAULT_PORT: u16 = 2222;
@@ -82,6 +83,13 @@ async fn main() {
     let config = Arc::new(config);
 
     let state = Arc::new(Mutex::new(game::GameState::new(loaded_world, db)));
+
+    // Spawn tick engine
+    let tick_state = state.clone();
+    tokio::spawn(async move {
+        tick::run_tick_engine(tick_state).await;
+    });
+
     let mut server = ssh::MudServer::new(state);
 
     let listener = TcpListener::bind(("0.0.0.0", port)).await.unwrap();