Add Helm chart, replace flux/ variable-substitution templates

Introduces chart/ with deployment, service, and PVC templates driven
by Helm values instead of Kustomize variable substitution. Removes
the flux/ directory which is superseded by the chart.

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>

chart/templates/pvc.yaml

@@ -0,0 +1,13 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: {{ include "antigravity.pvcName" . }}
+  labels:
+    {{- include "antigravity.labels" . | nindent 4 }}
+spec:
+  accessModes:
+    - ReadWriteMany
+  storageClassName: {{ .Values.storage.className }}
+  resources:
+    requests:
+      storage: {{ .Values.storage.size }}