feat(loot): add item, loot table, and combat reward entities

Declares every new TypeORM entity Slice 0.4 needs (ItemDefinition,
CharacterItem, LootTable, LootTableEntry, CombatReward, CombatRewardItem)
plus the ItemType/EquipmentSlot/ItemRarity enums, and adds the two columns
existing entities gain: Character.silver and MonsterDefinition.lootTableId.
No migration SQL or service logic yet - just schema declarations backed by
a metadata-driven schema spec.

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

apps/api/src/items/entities/item-definition.entity.ts

@@ -0,0 +1,74 @@
+import {
+  Column,
+  CreateDateColumn,
+  Entity,
+  Index,
+  PrimaryGeneratedColumn,
+  UpdateDateColumn,
+} from 'typeorm';
+import { EquipmentSlot } from '../equipment-slot.enum';
+import { ItemRarity } from '../item-rarity.enum';
+import { ItemType } from '../item-type.enum';
+
+@Entity({ name: 'item_definitions' })
+@Index('IDX_item_definitions_key', ['key'], { unique: true })
+export class ItemDefinition {
+  @PrimaryGeneratedColumn('uuid', { name: 'id' })
+  id!: string;
+
+  @Column({ name: 'key', type: 'varchar', length: 100 })
+  key!: string;
+
+  @Column({ name: 'name', type: 'varchar', length: 150 })
+  name!: string;
+
+  @Column({ name: 'description', type: 'text' })
+  description!: string;
+
+  @Column({ name: 'type', type: 'enum', enum: ItemType, enumName: 'item_type_enum' })
+  type!: ItemType;
+
+  @Column({
+    name: 'equipment_slot',
+    type: 'enum',
+    enum: EquipmentSlot,
+    enumName: 'equipment_slot_enum',
+    nullable: true,
+  })
+  equipmentSlot!: EquipmentSlot | null;
+
+  @Column({ name: 'rarity', type: 'enum', enum: ItemRarity, enumName: 'item_rarity_enum' })
+  rarity!: ItemRarity;
+
+  @Column({ name: 'tier', type: 'integer' })
+  tier!: number;
+
+  @Column({ name: 'required_level', type: 'integer' })
+  requiredLevel!: number;
+
+  @Column({ name: 'weapon_damage', type: 'integer' })
+  weaponDamage!: number;
+
+  @Column({ name: 'bonus_hp', type: 'integer' })
+  bonusHp!: number;
+
+  @Column({ name: 'bonus_attack', type: 'integer' })
+  bonusAttack!: number;
+
+  @Column({ name: 'bonus_armor', type: 'integer' })
+  bonusArmor!: number;
+
+  // Always 0 in Slice 0.4: there are no merchants, and the balancing doc's
+  // Grenzmarken table lists purchase prices, not sell prices.
+  @Column({ name: 'sell_price', type: 'integer' })
+  sellPrice!: number;
+
+  @Column({ name: 'icon_path', type: 'varchar', length: 255 })
+  iconPath!: string;
+
+  @CreateDateColumn({ name: 'created_at', type: 'timestamptz' })
+  createdAt!: Date;
+
+  @UpdateDateColumn({ name: 'updated_at', type: 'timestamptz' })
+  updatedAt!: Date;
+}