Make valkey local on ringtail (nix amd64) + bump to 8.1.7 (#362)

## Summary

Weekly "make one non-local container local" pickup: immich-ringtail still pulled `docker.io/valkey/valkey:8.1.6` because the existing `containers/valkey/container.py` build was arm64-only.

- Adds `containers/valkey/default.nix` — nix-built amd64 valkey image, packaged by the ringtail nix-container-builder runner using `pkgs.dockerTools.buildLayeredImage`. Mirrors the existing `containers/authentik-redis/default.nix` pattern.
- `containers/valkey/container.py` keeps building the Alpine arm64 image for paperless on indri. Bumped both builds to upstream valkey 8.1.7 (Alpine 3.22 now ships `8.1.7-r0`; nixpkgs has 8.1.7).
- Splits `VERSION` (upstream app) from `ALPINE_PIN` (apk pin) in `container.py` so both build files can declare the same upstream version and pass `container-version-check`.
- Updates `service-versions.yaml`: current-version 8.1.7, refreshed last-reviewed, upstream-source now points at the canonical valkey-io releases page.
- Switches kustomizations:
  - `immich-ringtail/kustomization.yaml`: `docker.io/valkey/valkey:8.1.6` → `registry.ops.eblu.me/blumeops/valkey:v8.1.7-02859c5-nix`, comment updated.
  - `paperless/kustomization.yaml`: `v8.1.6-r0-fabca04` → `v8.1.7-02859c5`.

## Build

build-container run #563 — both jobs succeeded after a transient runner crash on the first dispatch (#562 build-nix), which surfaced two separate bugs that landed in a separate C0 on main:

- `runner-logs` silently returned 0 with no output when the log file didn't exist on indri
- `ssh indri` swallowing remote exit codes (fish login shell), which the wrapper now works around via a stdout marker

## Test plan

- [ ] `argocd app set immich-ringtail --revision valkey-nix && argocd app sync immich-ringtail`
- [ ] `argocd app set paperless --revision valkey-nix && argocd app sync paperless`
- [ ] Both valkey pods come Ready and start serving on :6379
- [ ] Immich app + paperless can read/write their respective cache
- [ ] After merge: rebuild from squashed main commit + update kustomization tags (squash-tag follow-up)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #362

argocd/manifests/immich-ringtail/kustomization.yaml

@@ -21,8 +21,9 @@ images:
   - name: ghcr.io/immich-app/immich-machine-learning
     # CUDA variant of the same release — ringtail has an RTX 4080
     newTag: v2.6.3-cuda
-  # Using upstream multi-arch valkey image directly; the
-  # registry.ops.eblu.me/blumeops/valkey mirror is arm64-only (built
-  # on indri) and would crashloop on ringtail.
+  # amd64 valkey built via nix on the ringtail nix-container-builder
+  # (see containers/valkey/default.nix). The Alpine container.py build
+  # is arm64-only and serves paperless on indri.
   - name: docker.io/valkey/valkey
-    newTag: "8.1.6"
+    newName: registry.ops.eblu.me/blumeops/valkey
+    newTag: v8.1.7-02859c5-nix

argocd/manifests/paperless/kustomization.yaml

@@ -16,4 +16,4 @@ images:
     newTag: v2.20.13-07f52e9
   - name: docker.io/library/redis
     newName: registry.ops.eblu.me/blumeops/valkey
-    newTag: v8.1.6-r0-fabca04
+    newTag: v8.1.7-02859c5