feat: auth middleware, brain data layer, Valkey queue (P1-002/003/004) (#71)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/auth/current-user.decorator.ts

@@ -0,0 +1,7 @@
+import { createParamDecorator, type ExecutionContext } from '@nestjs/common';
+import type { FastifyRequest } from 'fastify';
+
+export const CurrentUser = createParamDecorator((_data: unknown, ctx: ExecutionContext) => {
+  const request = ctx.switchToHttp().getRequest<FastifyRequest & { user?: unknown }>();
+  return request.user;
+});