feat(combat): support a damage multiplier in calculateDamage

apps/api/src/combat/combat-damage.spec.ts

@@ -14,4 +14,13 @@ describe('calculateDamage', () => {
     // raw = 9; 9 * 60 / (60 + 5) = 8.307... -> rounds to 8
     expect(calculateDamage({ attack: 9 }, 5)).toBe(8);
   });
+
+  it('applies a damage multiplier before the minimum-1 floor', () => {
+    // raw = 27; mitigated = 20.25; *1.6 = 32.4 -> rounds to 32
+    expect(calculateDamage({ attack: 12, weaponDamage: 15 }, 20, 1.6)).toBe(32);
+  });
+
+  it('still floors at 1 damage even with a small multiplier', () => {
+    expect(calculateDamage({ attack: 1, weaponDamage: 0 }, 100_000, 0.5)).toBe(1);
+  });
 });