fix(SEC-ORCH-16): Implement real health and readiness checks

- Add ping() method to ValkeyClient and ValkeyService for health checks
- Update HealthService to check Valkey connectivity before reporting ready
- /health/ready now returns 503 if dependencies are unhealthy
- Add detailed checks object showing individual dependency status
- Update tests with ValkeyService mock

Refs #339

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/orchestrator/src/api/health/health.module.ts

@@ -1,8 +1,10 @@
 import { Module } from "@nestjs/common";
 import { HealthController } from "./health.controller";
 import { HealthService } from "./health.service";
+import { ValkeyModule } from "../../valkey/valkey.module";
 
 @Module({
+  imports: [ValkeyModule],
   controllers: [HealthController],
   providers: [HealthService],
 })