feat(paperless-ngx): optional valkey subchart, password from the redis item

paperless-ngx cannot run without a Redis - PAPERLESS_REDIS is the Celery
broker - so every installation needed a second Helm release whose address
lived in a 1Password item and in neither chart. This adds our own published
valkey chart as an optional dependency, off by default and gated on
valkeySubchart.enabled (not valkey.enabled, which the subchart's strict
schema rejects and which Helm would only have complained about for whoever
first switched it on). Additive, default behaviour unchanged: minor,
12.1.3+up3.2.1 -> 12.2.0+up3.2.1.

Configured as a QUEUE (PVC + noeviction, the subchart's defaults), unlike
stalwart's cache. Read off the 3.2.1 source rather than assumed: one
PAPERLESS_REDIS url serves five consumers - the Celery broker, the result
backend (Redis in 3.x, the database before), the channels pub/sub layer and
two Django caches. allkeys-lru would not be a trade here but actively wrong,
because LRU evicts typeless across the whole keyspace and a backlog of
waiting consume tasks is exactly what it reads as cold; a dropped task is a
document silently never processed. The price, named in values.yaml rather
than smoothed over: two of the five consumers are caches, so a full instance
refuses writes - new tasks included - and the answer is memory sizing, not a
policy change. All three cache-like consumers are TTL-bounded, which is what
keeps that price small.

The password comes from the SAME item as the Redis connection, in a third
field auth-conf holding the complete line "requirepass <password>". It cannot
DEFAULT to secrets.redisSecretRef, and that is a property of Helm, not an
omission: a values.yaml is never templated and a parent cannot compute a
subchart's value. Measured - a template expression there lands verbatim in
the subchart's itemPath and fails as a YAML parse error naming neither the
value nor the cause.

Forgetting it is therefore caught in values.schema.json, by a conditional
rule rather than a fail() in a template. Also measured, and the reason:
Helm renders a subchart's templates BEFORE the parent's, so a guard in this
chart loses the race to the subchart's own required(), which reports
"secrets.authSecretRef" and cannot know the path belongs to the redis item.
A check that cannot fire is the mistake found while testing #77, so the
first draft of that guard was removed rather than shipped. The schema runs
before any rendering and names /valkey/secrets/authSecretRef.

One trap found while testing and closed here: "valkeySubchart: null" DELETES
the key, Helm then cannot resolve the condition path and treats the
dependency as ENABLED - so erasing the switch turned the subchart on with no
password set. Unlike every other block in this chart (issue #99), that one
is rejected by the schema instead of defaulting.

The install-test now runs with the subchart ON and the throwaway redis
Deployment removed: the url in the fixtures names ci-valkey-service, so the
bundled Valkey is the broker the release actually uses. #65 covered this
path by a render only - deliberately, since an unused Valkey would have made
that test look like it covered clustering. This is the first real
installation of the valkey-subchart path.

Documented, not glossed: the password now sits in that item twice and a
rotation has to touch both fields; with the subchart on the vault url is a
mandatory step, not a hint; and a OnePasswordItem materializes every field
of its item, so both Secrets carry all three keys - untidy, harmless, and
written down so nobody "tidies it up".

Fixes #78

paperless-ngx/values.schema.json

@@ -4,6 +4,48 @@
   "description": "Strict values schema (issue #68). additionalProperties is false on every chart-owned object level, so a key that the chart does not read is rejected at render time instead of being silently ignored. The only objects that stay open are the ones passed verbatim into the Kubernetes pod spec (probes, security contexts, global) - the chart does not interpret their contents, so it cannot judge which keys are meaningful. The hardening, probe and resources blocks of BOTH workloads, and the barcodes block from issue #61, additionally accept null, because an erased block falls back to the chart defaults (issues #61 and #99).",
   "type": "object",
   "additionalProperties": false,
+  "required": ["valkeySubchart"],
+  "allOf": [
+    {
+      "title": "With the valkey subchart switched on, valkey.secrets.authSecretRef is required",
+      "description": "The one cross-key rule in this file, and it lives here rather than in a template on purpose: Helm validates the schema BEFORE it renders anything, and it renders a subchart's templates before the parent's. A fail() in this chart's templates therefore loses the race against the subchart's own required(), whose message names 'secrets.authSecretRef' and cannot know that the path belongs to the same 1Password item as secrets.redisSecretRef. Measured for Gitea #78 - a guard that cannot fire is the mistake found while testing #77. Set it to the SAME op:// path as secrets.redisSecretRef: the bundled Valkey reads its password from the field 'auth-conf' in that item, whose value must be the complete line 'requirepass <password>'. A different item is allowed; two items then have to be kept in step.",
+      "if": {
+        "required": ["valkeySubchart"],
+        "properties": {
+          "valkeySubchart": {
+            "type": "object",
+            "required": ["enabled"],
+            "properties": {
+              "enabled": {
+                "const": true
+              }
+            }
+          }
+        }
+      },
+      "then": {
+        "required": ["valkey"],
+        "properties": {
+          "valkey": {
+            "type": "object",
+            "required": ["secrets"],
+            "properties": {
+              "secrets": {
+                "type": "object",
+                "required": ["authSecretRef"],
+                "properties": {
+                  "authSecretRef": {
+                    "type": "string",
+                    "minLength": 1
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  ],
   "properties": {
     "global": {
       "description": "Helm's conventional cross-chart values. Unused by this chart, kept open so an umbrella install cannot break on it.",
@@ -261,6 +303,21 @@
           }
         }
       }
+    },
+    "valkeySubchart": {
+      "description": "The dependency condition for the valkey subchart. A key of THIS chart, deliberately outside the 'valkey' subtree: everything under 'valkey:' is handed to the subchart as its values, and this repo's valkey chart has additionalProperties: false with no 'enabled' property, so 'valkey.enabled' is rejected by the subchart itself. Helm skips a disabled subchart's schema validation, so that error would only ever have surfaced for whoever first set it to true. NOT null-safe and 'enabled' is REQUIRED, which is the opposite of this chart's other blocks (issue #99) and is deliberate: Helm treats a condition whose path does not resolve as ENABLED, so an erased 'valkeySubchart:' would switch the subchart ON - measured for Gitea #78, where it surfaced as the subchart's own required() error. An erased block must not flip behaviour, least of all in that direction, so it is rejected here instead.",
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["enabled"],
+      "properties": {
+        "enabled": {
+          "type": "boolean"
+        }
+      }
+    },
+    "valkey": {
+      "description": "Values passed through to the valkey subchart - this repo's OWN valkey chart, resolved from the published index. Open on purpose and at every level: the subchart owns this schema (it ships its own, and a stricter one than this), and a closed copy here would reject whatever that chart adds in its next release while duplicating a validation that already happens. This chart reads NONE of these keys; the dependency condition is valkeySubchart.enabled instead. Two shapes that are easy to get wrong: secrets.authSecretRef must be set BY HAND to the same op:// path as secrets.redisSecretRef (a values.yaml is never templated, so a parent cannot default it - Gitea #78), and the item's field 'auth-conf' holds the complete line 'requirepass <password>', not a bare password. values.yaml argues the queue-vs-cache choice and names the three operator traps.",
+      "type": "object"
     }
   },
   "definitions": {