Kubernetes Network Policies

Create Kubernetes network policies for my cluster.

Cluster architecture:
- Namespaces: [list namespaces]
- Services per namespace: [describe services]
- External dependencies: [databases, APIs]
- Ingress controller: [nginx/istio/etc.]

Network requirements:
1. Default deny all traffic
2. Allow specific ingress patterns
3. Allow specific egress patterns
4. Cross-namespace communication rules
5. External service access
6. DNS policy configuration

Specific rules needed:
- Frontend -> Backend communication
- Backend -> Database access
- Backend -> External API access
- Monitoring namespace access
- Ingress controller rules

Please include:
- Network policy manifests
- Testing procedures
- Troubleshooting guide
- Visualization of traffic flow