feat: als and prisma

core/als/request-context.service.ts

@@ -0,0 +1,48 @@
+import { Injectable } from '@nestjs/common';
+import { AsyncLocalStorage } from 'async_hooks';
+import { RequestContext } from './request-context.type';
+
+@Injectable()
+/**
+ * RequestContext holds per-request metadata including:
+ * - HTTP request
+ * - Auth payload (decoded JWT, optional)
+ * - Prisma transaction client (optional)
+ * - Correlation ID and other future cross-cutting concerns
+ */
+export class RequestContextService {
+  private readonly als = new AsyncLocalStorage<RequestContext>();
+
+  run(context: RequestContext, fn: () => void) {
+    this.als.run(context, fn);
+  }
+
+  get(): RequestContext {
+    const store = this.als.getStore();
+    if (!store) {
+      throw new Error('RequestContext not initialized');
+    }
+    return store;
+  }
+
+  set<K extends keyof RequestContext>(key: K, value: RequestContext[K]) {
+    this.get()[key] = value;
+  }
+
+  // Helpers
+  get user() {
+    return this.get().user;
+  }
+
+  get tx() {
+    return this.get().tx;
+  }
+
+  set tx(tx) {
+    this.set('tx', tx);
+  }
+
+  get isTransaction(): boolean {
+    return !!this.get().tx;
+  }
+}