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/world.rs

@@ -49,7 +49,7 @@ impl Attitude {
         matches!(self, Attitude::Hostile)
     }
 
-    pub fn can_be_attacked(self) -> bool {
+    pub fn is_hostile(self) -> bool {
         matches!(self, Attitude::Hostile | Attitude::Aggressive)
     }
 
@@ -315,7 +315,8 @@ impl World {
 
             load_entities_from_dir(&region_path.join("npcs"), &region_name, &mut |id, content| {
                 let nf: NpcFile = toml::from_str(content).map_err(|e| format!("Bad npc {id}: {e}"))?;
-                let combat = nf.combat.map(|c| NpcCombatStats { max_hp: c.max_hp, attack: c.attack, defense: c.defense, xp_reward: c.xp_reward });
+                let combat = Some(nf.combat.map(|c| NpcCombatStats { max_hp: c.max_hp, attack: c.attack, defense: c.defense, xp_reward: c.xp_reward })
+                    .unwrap_or(NpcCombatStats { max_hp: 20, attack: 4, defense: 2, xp_reward: 5 }));
                 let greeting = nf.dialogue.and_then(|d| d.greeting);
                 npcs.insert(id.clone(), Npc { id: id.clone(), name: nf.name, description: nf.description, room: nf.room, base_attitude: nf.base_attitude, faction: nf.faction, respawn_secs: nf.respawn_secs, greeting, combat });
                 Ok(())