feat(gateway): MosaicPlugin lifecycle + ReloadService + hot reload (P8-013)

Implements gateway hot reload via MosaicPlugin interface, ReloadService orchestration,
/reload admin command, POST /api/admin/reload REST endpoint, SIGHUP handler, and
system:reload broadcast to all connected TUI clients via ChatGateway.

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

apps/gateway/src/reload/reload.module.ts

@@ -0,0 +1,14 @@
+import { forwardRef, Module } from '@nestjs/common';
+import { AdminGuard } from '../admin/admin.guard.js';
+import { ChatModule } from '../chat/chat.module.js';
+import { CommandsModule } from '../commands/commands.module.js';
+import { ReloadController } from './reload.controller.js';
+import { ReloadService } from './reload.service.js';
+
+@Module({
+  imports: [forwardRef(() => CommandsModule), forwardRef(() => ChatModule)],
+  controllers: [ReloadController],
+  providers: [ReloadService, AdminGuard],
+  exports: [ReloadService],
+})
+export class ReloadModule {}