## Changes
- Upgrade external-dns chart from 1.19.0 → 1.21.1 (app v0.19.0 → v0.21.0)
- Remove `gateway-tcproute` source — `TCPRoute` CRD is not installed, causing crash-loop
- Add `gateway-tlsroute` source — `TLSRoute` CRD is installed (Gateway API 1.5.1)
## Why
The pod was crash-looping every minute with `failed to list *v1alpha2.TCPRoute: the server could not find the requested resource` because the TCPRoute CRD doesn't exist in this cluster. TLSRoute was previously removed but its CRD does exist.
Reviewed-on: #143
- Add externaldns base ArgoCD application with namespace and Vault integration
- Create externaldns overlay for au-syd1 with Helm chart configuration
- Update platform ApplicationSet to include externaldns deployment
- Configure external-dns v1.19.0 with RFC2136 provider for DNS updates
- Maintain one-to-one migration from Terraform configuration including TSIG secrets
Reviewed-on: #43
unkinben