Set 429 status code responses in the config map (#849)

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## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
Seems that per ingress annotations were not working, so had to put them
in the ingress configmap. Did tested this manually on staging so it's
confirmed it's working (I was getting 429s instead of 503s) and no
traffic was getting into the registry pod.
 
## How Has This Been Tested?
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tested? -->

## Breaking Changes
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## Types of changes
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the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
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that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
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Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

deploy/pkg/k8s/ingress.go

@@ -74,6 +74,9 @@ func SetupIngressController(ctx *pulumi.Context, cluster *providers.ProviderInfo
 					// GCP L4 Passthrough Network Load Balancer does not set X-Forwarded-For
 					// Real client IP comes from TCP connection source with externalTrafficPolicy: Local
 					"use-forwarded-headers": pulumi.String("false"),
+
+					// Set rate limit rejection status code to 429 (Too Many Requests)
+					"limit-req-status-code": pulumi.String("429"),
 				},
 			},
 		},

deploy/pkg/k8s/registry.go

@@ -248,9 +248,9 @@ func DeployMCPRegistry(ctx *pulumi.Context, cluster *providers.ProviderInfo, env
 				"kubernetes.io/ingress.class":    pulumi.String("nginx"),
 			// Rate limiting to protect against abuse
 			// Allows 180 requests/minute (3 req/sec avg), with bursts up to 540 requests
+			// Status code 429 is set globally via NGINX ConfigMap (per-Ingress annotation doesn't work)
 			"nginx.ingress.kubernetes.io/limit-rpm":              pulumi.String("180"),
 			"nginx.ingress.kubernetes.io/limit-burst-multiplier": pulumi.String("3"),
-			"nginx.ingress.kubernetes.io/limit-req-status-code":  pulumi.String("429"),
 			},
 		},
 		Spec: &networkingv1.IngressSpecArgs{