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/monsters/entities/monster-definition.entity.ts

@@ -3,9 +3,12 @@ import {
   CreateDateColumn,
   Entity,
   Index,
+  JoinColumn,
+  ManyToOne,
   PrimaryGeneratedColumn,
   UpdateDateColumn,
 } from 'typeorm';
+import { LootTable } from '../../loot/entities/loot-table.entity';
 
 @Entity({ name: 'monster_definitions' })
 @Index('IDX_monster_definitions_key', ['key'], { unique: true })
@@ -43,9 +46,16 @@ export class MonsterDefinition {
   @Column({ name: 'artwork_path', type: 'varchar', length: 255 })
   artworkPath!: string;
 
+  @Column({ name: 'loot_table_id', type: 'uuid', nullable: true })
+  lootTableId!: string | null;
+
   @CreateDateColumn({ name: 'created_at', type: 'timestamptz' })
   createdAt!: Date;
 
   @UpdateDateColumn({ name: 'updated_at', type: 'timestamptz' })
   updatedAt!: Date;
+
+  @ManyToOne(() => LootTable, { onDelete: 'RESTRICT', nullable: true })
+  @JoinColumn({ name: 'loot_table_id' })
+  lootTable!: LootTable | null;
 }