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

CLAUDE.md

@@ -117,4 +117,4 @@ The binding style guide for all current and future charts lives in **README.md (
 - Resources: requests as values defaults; limits auto-computed by the `_helpers.tpl` helper (`limitFactor` default 3; no CPU limits unless set explicitly).
 - Replicas per workload (explicit `0` allowed) plus a chart-global `scaleDown` flag that overrides them.
 - `icon:` mandatory in every `Chart.yaml`; `helm lint --strict` without findings; CI fixtures under `ci/<chart>/` or a justified exclusion.
-- **Chart dependencies are admissible but expensive** (the former "no dependencies" rule fell with #214; `ytdlp-web-player` was the first to use one, `stalwart` the second). A dependency has to be optional and off by default via `condition:`, and upstream's chart is consumed as it comes — where its defaults fall short of these conventions, that is **documented in our `values.yaml`, never patched**. The price to know before adding the next one: a subchart is invisible to everything downstream that watches Helm release versions, so a new upstream version — a security fix included — reaches a cluster only when the outer chart is republished (Renovate's built-in `helmv3` manager plus `ci/renovate-bump-chart.sh` is the whole safety net, and it belongs in a comment at the pinned version); and every helm command exits 1 while `charts/` is unfilled, which is why `ci/helm-dependencies.sh` runs before lint, package, render and install — including the render test that covers **all** charts on **every** PR. Full rules and the rest of the cost: README, "Chart dependencies".
+- **Chart dependencies are admissible but expensive** (the former "no dependencies" rule fell with #214; `ytdlp-web-player` was the first to use one, `stalwart` the second, `paperless-ngx` the third). A dependency has to be optional and off by default via `condition:`, and upstream's chart is consumed as it comes — where its defaults fall short of these conventions, that is **documented in our `values.yaml`, never patched**. The price to know before adding the next one: a subchart is invisible to everything downstream that watches Helm release versions, so a new upstream version — a security fix included — reaches a cluster only when the outer chart is republished (Renovate's built-in `helmv3` manager plus `ci/renovate-bump-chart.sh` is the whole safety net, and it belongs in a comment at the pinned version); and every helm command exits 1 while `charts/` is unfilled, which is why `ci/helm-dependencies.sh` runs before lint, package, render and install — including the render test that covers **all** charts on **every** PR. Full rules and the rest of the cost: README, "Chart dependencies".