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/valkey/valkey.client.ts

@@ -71,6 +71,19 @@ export class ValkeyClient {
     }
   }
 
+  /**
+   * Check Valkey connectivity
+   * @returns true if connection is healthy, false otherwise
+   */
+  async ping(): Promise<boolean> {
+    try {
+      await this.client.ping();
+      return true;
+    } catch {
+      return false;
+    }
+  }
+
   /**
    * Task State Management
    */

apps/orchestrator/src/valkey/valkey.service.ts

@@ -152,4 +152,12 @@ export class ValkeyService implements OnModuleDestroy {
     };
     await this.setAgentState(state);
   }
+
+  /**
+   * Check Valkey connectivity
+   * @returns true if connection is healthy, false otherwise
+   */
+  async ping(): Promise<boolean> {
+    return this.client.ping();
+  }
 }