cyberchef: honour ingress.enabled, add null-safe hardening

Three changes, all about values that do not do what they promise:

1. Ingress gate (#93): the Ingress template is wrapped in
   {{- if .Values.ingress.enabled }}. The key already existed in
   values.yaml with default true but was never read, so switching it off
   did nothing. Both required() calls for domain and clusterIssuer live
   inside the Ingress file, so gating also removes the contradiction that
   one had to supply a domain and issuer in order to turn off an Ingress
   one does not want.

2. Null-safety for hardening, probes and resources (#99): an override
   written without children is YAML null and erased the whole default
   sub-tree, rendering "securityContext: null" - an unhardened container
   that starts and reports healthy.

3. values.schema.json types (#68 + #99): the blocks covered by the
   null-safety accept null. This is load-bearing only for keys that have
   no chart default (e.g. resources.limits): there Helm has nothing to
   delete, so the null survives into schema validation and a strict
   "object" type rejected it outright.

Rendering with normal values is byte-identical to 7.0.0.

cyberchef/values.schema.json

@@ -65,7 +65,8 @@
   },
   "definitions": {
     "resources": {
-      "type": "object",
+      "description": "May be null / empty: the chart then falls back to its default requests and computed limits (issue #99) instead of rendering a container without resource accounting.",
+      "type": ["object", "null"],
       "additionalProperties": false,
       "properties": {
         "limitFactor": {
@@ -81,7 +82,7 @@
       }
     },
     "resourceList": {
-      "type": "object",
+      "type": ["object", "null"],
       "additionalProperties": false,
       "properties": {
         "cpu": {
@@ -140,22 +141,23 @@
       }
     },
     "securityContext": {
-      "type": "object",
+      "description": "May be null / empty at any level: the chart then falls back to its hardening defaults (issue #99) instead of rendering an unhardened workload.",
+      "type": ["object", "null"],
       "additionalProperties": false,
       "properties": {
         "pod": {
-          "description": "Rendered verbatim as the pod's securityContext; kept open because the chart does not interpret it.",
-          "type": "object"
+          "description": "Merged onto the chart's pod hardening defaults and rendered as the pod's securityContext; kept open because the chart does not interpret the individual fields.",
+          "type": ["object", "null"]
         },
         "container": {
-          "description": "Rendered verbatim as the container's securityContext; kept open because the chart does not interpret it.",
-          "type": "object"
+          "description": "Merged onto the chart's container hardening defaults and rendered as the container's securityContext; kept open because the chart does not interpret the individual fields.",
+          "type": ["object", "null"]
         }
       }
     },
     "probe": {
-      "description": "Rendered verbatim as a container probe; kept open because the chart does not interpret it.",
-      "type": "object"
+      "description": "Merged onto the chart's probe defaults and rendered as a container probe; kept open because the chart does not interpret the individual fields. May be null / empty, which means the defaults apply (issue #99) rather than the probe disappearing.",
+      "type": ["object", "null"]
     }
   }
 }