feat(chart/electric): expose extraVolumes/extraVolumeMounts

Adds `electric.extraVolumes` and `electric.extraVolumeMounts` (same
pattern as webapp/supervisor) so operators can:

  - Provide the writable `/app/persistent` mount Electric requires at
    runtime (as an emptyDir, PVC, etc.) — previously the chart had no
    knob for this.
  - Mount additional volumes such as enterprise CA bundles for TLS
    validation against private registries or Postgres.

Defaults are empty lists, preserving current behavior.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: ConProgramming

hosting/k8s/helm/values.yaml

@@ -572,6 +572,27 @@ electric:
     # - name: CUSTOM_VAR
     #   value: "custom-value"
 
+  # Extra volumes added to the Electric pod. Use cases include providing
+  # the `/app/persistent` mount Electric needs at runtime (e.g. as an
+  # emptyDir or PVC), or mounting an enterprise CA bundle.
+  extraVolumes:
+    []
+    # - name: persistent
+    #   emptyDir: {}
+    # - name: ca-bundle
+    #   configMap:
+    #     name: enterprise-ca-bundle
+
+  # Extra volume mounts added to the Electric container. Pair with the
+  # corresponding entries in `extraVolumes`.
+  extraVolumeMounts:
+    []
+    # - name: persistent
+    #   mountPath: /app/persistent
+    # - name: ca-bundle
+    #   mountPath: /etc/ssl/enterprise-ca
+    #   readOnly: true
+
 # ClickHouse configuration
 # Subchart: https://github.com/bitnami/charts/tree/main/bitnami/clickhouse
 clickhouse: