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/rewards/entities/combat-reward-item.entity.ts

@@ -0,0 +1,56 @@
+import {
+  Column,
+  CreateDateColumn,
+  Entity,
+  Index,
+  JoinColumn,
+  ManyToOne,
+  PrimaryGeneratedColumn,
+} from 'typeorm';
+import { CharacterItem } from '../../items/entities/character-item.entity';
+import { ItemDefinition } from '../../items/entities/item-definition.entity';
+import { CombatReward } from './combat-reward.entity';
+
+/**
+ * What this specific combat dropped.
+ *
+ * Needed because `CharacterItem.quantity` is a running stack total: after a
+ * duplicate drop it no longer says how much *this* victory granted, and a
+ * refreshed reward screen must replay the original result (spec §25, §48).
+ */
+@Entity({ name: 'combat_reward_items' })
+@Index('IDX_combat_reward_items_reward', ['combatRewardId'])
+@Index('IDX_combat_reward_items_reward_item', ['combatRewardId', 'itemDefinitionId'], {
+  unique: true,
+})
+export class CombatRewardItem {
+  @PrimaryGeneratedColumn('uuid', { name: 'id' })
+  id!: string;
+
+  @Column({ name: 'combat_reward_id', type: 'uuid' })
+  combatRewardId!: string;
+
+  @Column({ name: 'character_item_id', type: 'uuid' })
+  characterItemId!: string;
+
+  @Column({ name: 'item_definition_id', type: 'uuid' })
+  itemDefinitionId!: string;
+
+  @Column({ name: 'quantity', type: 'integer' })
+  quantity!: number;
+
+  @CreateDateColumn({ name: 'created_at', type: 'timestamptz' })
+  createdAt!: Date;
+
+  @ManyToOne(() => CombatReward, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'combat_reward_id' })
+  combatReward!: CombatReward;
+
+  @ManyToOne(() => CharacterItem, { onDelete: 'RESTRICT' })
+  @JoinColumn({ name: 'character_item_id' })
+  characterItem!: CharacterItem;
+
+  @ManyToOne(() => ItemDefinition, { onDelete: 'RESTRICT' })
+  @JoinColumn({ name: 'item_definition_id' })
+  itemDefinition!: ItemDefinition;
+}