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/modules/loot/dto/apply-loot-profile.dto.ts

@@ -0,0 +1,9 @@
+import { IsNumber, IsIn } from 'class-validator';
+import { ApiProperty } from '@nestjs/swagger';
+
+export class ApplyLootProfileDto {
+  @ApiProperty({ example: 1, description: 'Loot multiplier', enum: [1, 2, 5, 10] })
+  @IsNumber()
+  @IsIn([1, 2, 5, 10])
+  multiplier: number;
+}