feat: Add loot builder backend + static data + DB migration

- Migration 013: loot_profiles table (JSONB loot_table + loot_groups, license-scoped)
- TypeORM entity matching migration schema exactly
- NestJS loot module: 10 endpoints (CRUD, duplicate, apply, import, export, containers)
- Multiplier logic recursively scales Min/Max/Scrap across loot tables and groups
- Apply-to-server writes BetterLoot JSON via NATS file manager + RCON reload
- Frontend static data: 191 Rust items, 51 container prefabs
- TypeScript types for BetterLoot data model (PrefabLoot, LootEntry, LootRNG, etc.)
- Fix vue-tsc errors: UngroupedItems uses LootRNG, null safety in store/view

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-nest/src/entities/loot-profile.entity.ts

@@ -0,0 +1,36 @@
+import { Entity, PrimaryGeneratedColumn, Column, ManyToOne, JoinColumn } from 'typeorm';
+import { License } from './license.entity';
+
+@Entity('loot_profiles')
+export class LootProfile {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column({ type: 'uuid' })
+  license_id: string;
+
+  @Column({ type: 'varchar', length: 100 })
+  profile_name: string;
+
+  @Column({ type: 'text', nullable: true })
+  description: string | null;
+
+  @Column({ type: 'jsonb', default: () => "'{}'" })
+  loot_table: Record<string, any>;
+
+  @Column({ type: 'jsonb', default: () => "'{}'" })
+  loot_groups: Record<string, any>;
+
+  @Column({ type: 'boolean', default: false })
+  is_active: boolean;
+
+  @Column({ type: 'timestamptz', default: () => 'NOW()' })
+  created_at: Date;
+
+  @Column({ type: 'timestamptz', default: () => 'NOW()' })
+  updated_at: Date;
+
+  @ManyToOne(() => License, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'license_id' })
+  license: License;
+}