chore: set version to v0.4.0

Author: github-actions[bot]

CHANGELOG.md

@@ -0,0 +1,17 @@
+### What's changed in v0.4.0
+
+* feat: add ExternalDNS Gateway API source alongside Istio (by @patrickleet)
+
+  Adds spec.externalDNS.gatewayApi.enabled (default false). When true,
+  ExternalDNS additionally watches Gateway API HTTPRoutes (and their parent
+  Gateways for host inheritance) so Knative-on-Gateway-API and any other
+  HTTPRoute-fronted services auto-publish per-host DNS records.
+
+  Existing spec.externalDNS.istio.enabled is unchanged. Both toggles are
+  independent and additive — useful during a migration period when both
+  VirtualServices and HTTPRoutes are in flight.
+
+  Implements [[tasks/dns-stack-gateway-api-source]]
+
+
+See full diff: [v0.3.0...v0.4.0](https://github.com/hops-ops/cloudflare-dns-stack/compare/v0.3.0...v0.4.0)