feat: Add Kits + FurnaceSplitter plugin config modules

DB migrations 016 (kits_configs) and 019 (furnacesplitter_configs) applied.
Backend: NestJS modules with CRUD, apply-to-server, import-from-server.
Frontend: Pinia stores, Vue views with config editor, router + nav wiring.
Kits view: 3-tab editor (list/editor/settings), kit items with shortname/amount/skinId/container.
FurnaceSplitter view: per-furnace toggles, split count, fuel multiplier settings.

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

backend-nest/src/modules/furnacesplitter/furnacesplitter.module.ts

@@ -0,0 +1,14 @@
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { FurnaceSplitterController } from './furnacesplitter.controller';
+import { FurnaceSplitterService } from './furnacesplitter.service';
+import { FurnaceSplitterConfig } from '../../entities/furnacesplitter-config.entity';
+import { NatsService } from '../../services/nats.service';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([FurnaceSplitterConfig])],
+  controllers: [FurnaceSplitterController],
+  providers: [FurnaceSplitterService, NatsService],
+  exports: [FurnaceSplitterService],
+})
+export class FurnaceSplitterModule {}