Show AC on each tracker row

Combatant snapshots armor_class from the enemy when added (like maxHp),
shown as an "AC n" pill next to the name for quick hit checks. Migration
backfills existing combatants from their enemy.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Entity/Combatant.php

@@ -30,6 +30,9 @@ class Combatant
     #[ORM\Column(length: 120)]
     private string $label = '';
 
+    #[ORM\Column(type: Types::SMALLINT)]
+    private int $armorClass = 10;
+
     #[ORM\Column(type: Types::SMALLINT)]
     private int $maxHp = 1;
 
@@ -113,6 +116,18 @@ class Combatant
         return $this;
     }
 
+    public function getArmorClass(): int
+    {
+        return $this->armorClass;
+    }
+
+    public function setArmorClass(int $armorClass): static
+    {
+        $this->armorClass = $armorClass;
+
+        return $this;
+    }
+
     public function getMaxHp(): int
     {
         return $this->maxHp;