feat(api): integrate equipment stats into combat damage system

Equipment-Combat Integration:
- Update Stats damage formula from STR//2 to int(STR*0.75) for better scaling
- Add spell_power system for magical weapons (staves, wands)
- Add spell_power_bonus field to Stats model with spell_power property
- Add spell_power field to Item model with is_magical_weapon() method
- Update Character.get_effective_stats() to populate spell_power_bonus

Combatant Model Updates:
- Add weapon property fields (crit_chance, crit_multiplier, damage_type)
- Add elemental weapon support (elemental_damage_type, physical_ratio, elemental_ratio)
- Update serialization to handle new weapon properties

DamageCalculator Refactoring:
- Remove weapon_damage parameter from calculate_physical_damage()
- Use attacker_stats.damage directly (includes weapon bonus)
- Use attacker_stats.spell_power for magical damage calculations

Combat Service Updates:
- Extract weapon properties in _create_combatant_from_character()
- Use stats.damage_bonus for enemy combatants from templates
- Remove hardcoded _get_weapon_damage() method
- Handle elemental weapons with split damage in _execute_attack()

Item Generation Updates:
- Add base_spell_power to BaseItemTemplate dataclass
- Add ARCANE damage type to DamageType enum
- Add magical weapon templates (wizard_staff, arcane_staff, wand, crystal_wand)

Test Updates:
- Update test_stats.py for new damage formula (0.75 scaling)
- Update test_character.py for equipment bonus calculations
- Update test_damage_calculator.py for new API signatures
- Update test_combat_service.py mock fixture for equipped attribute

Tests: 174 passing

api/app/models/combat.py

@@ -12,7 +12,7 @@ import random
 from app.models.stats import Stats
 from app.models.effects import Effect
 from app.models.abilities import Ability
-from app.models.enums import CombatStatus, EffectType
+from app.models.enums import CombatStatus, EffectType, DamageType
 
 
 @dataclass
@@ -36,6 +36,12 @@ class Combatant:
         abilities: Available abilities for this combatant
         cooldowns: Map of ability_id to turns remaining
         initiative: Turn order value (rolled at combat start)
+        weapon_crit_chance: Critical hit chance from equipped weapon
+        weapon_crit_multiplier: Critical hit damage multiplier
+        weapon_damage_type: Primary damage type of weapon
+        elemental_damage_type: Secondary damage type for elemental weapons
+        physical_ratio: Portion of damage that is physical (0.0-1.0)
+        elemental_ratio: Portion of damage that is elemental (0.0-1.0)
     """
 
     combatant_id: str
@@ -51,6 +57,16 @@ class Combatant:
     cooldowns: Dict[str, int] = field(default_factory=dict)
     initiative: int = 0
 
+    # Weapon properties (for combat calculations)
+    weapon_crit_chance: float = 0.05
+    weapon_crit_multiplier: float = 2.0
+    weapon_damage_type: Optional[DamageType] = None
+
+    # Elemental weapon properties (for split damage)
+    elemental_damage_type: Optional[DamageType] = None
+    physical_ratio: float = 1.0
+    elemental_ratio: float = 0.0
+
     def is_alive(self) -> bool:
         """Check if combatant is still alive."""
         return self.current_hp > 0
@@ -228,6 +244,12 @@ class Combatant:
             "abilities": self.abilities,
             "cooldowns": self.cooldowns,
             "initiative": self.initiative,
+            "weapon_crit_chance": self.weapon_crit_chance,
+            "weapon_crit_multiplier": self.weapon_crit_multiplier,
+            "weapon_damage_type": self.weapon_damage_type.value if self.weapon_damage_type else None,
+            "elemental_damage_type": self.elemental_damage_type.value if self.elemental_damage_type else None,
+            "physical_ratio": self.physical_ratio,
+            "elemental_ratio": self.elemental_ratio,
         }
 
     @classmethod
@@ -236,6 +258,15 @@ class Combatant:
         stats = Stats.from_dict(data["stats"])
         active_effects = [Effect.from_dict(e) for e in data.get("active_effects", [])]
 
+        # Parse damage types
+        weapon_damage_type = None
+        if data.get("weapon_damage_type"):
+            weapon_damage_type = DamageType(data["weapon_damage_type"])
+
+        elemental_damage_type = None
+        if data.get("elemental_damage_type"):
+            elemental_damage_type = DamageType(data["elemental_damage_type"])
+
         return cls(
             combatant_id=data["combatant_id"],
             name=data["name"],
@@ -249,6 +280,12 @@ class Combatant:
             abilities=data.get("abilities", []),
             cooldowns=data.get("cooldowns", {}),
             initiative=data.get("initiative", 0),
+            weapon_crit_chance=data.get("weapon_crit_chance", 0.05),
+            weapon_crit_multiplier=data.get("weapon_crit_multiplier", 2.0),
+            weapon_damage_type=weapon_damage_type,
+            elemental_damage_type=elemental_damage_type,
+            physical_ratio=data.get("physical_ratio", 1.0),
+            elemental_ratio=data.get("elemental_ratio", 0.0),
         )