chore(repo): restructure as monorepo with server and client workspaces

- move NestJS app into server/ subdirectory
- add client/ React+TypeScript (Vite) app with Hello World
- update docker-compose to build and run both services
- add root package.json declaring npm workspaces
- update .gitignore to cover node_modules and dist at all depths

server/src/session/session.module.ts

@@ -0,0 +1,15 @@
+import { Module } from "@nestjs/common";
+import { TypeOrmModule } from "@nestjs/typeorm";
+import { SessionEntity } from "./session.entity";
+import { SessionService } from "./session.service";
+import { SessionController } from "./session.controller";
+import { SessionContextService } from "./session-context.service";
+import { SessionSchedulerService } from "./session-scheduler.service";
+
+@Module({
+  imports: [TypeOrmModule.forFeature([SessionEntity])],
+  controllers: [SessionController],
+  providers: [SessionService, SessionContextService, SessionSchedulerService],
+  exports: [SessionService, SessionContextService],
+})
+export class SessionModule {}