fix: Replace Ingress with HTTPRoute (Gateway API)

Switch from Ingress to HTTPRoute for Gateway API compatibility.

Changes:
- Remove k8s/ingress.yaml
- Add k8s/httproute.yaml with Gateway API configuration
- Update kustomization.yaml to reference httproute.yaml
- Update README.md references from Ingress to HTTPRoute

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

k8s/httproute.yaml

@@ -0,0 +1,20 @@
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: antigravity
+spec:
+  parentRefs:
+  - name: gateway  # Replace with your Gateway name
+    namespace: gateway-system  # Replace with your Gateway namespace
+  hostnames:
+  - "antigravity.example.com"  # Replace with your domain
+  rules:
+  - matches:
+    - path:
+        type: PathPrefix
+        value: /
+    backendRefs:
+    - name: antigravity
+      port: 5800
+      weight: 1