Harden zot registry, pt 1 (#231)

## Summary
- Enable OIDC + API key authentication on zot with anonymous pull preserved
- Enforce tag immutability for version tags
- Adopt commit-SHA-based container image tagging

Details in the [[harden-zot-registry]] Mikado chain (`mise run docs-mikado harden-zot-registry`).

## Test plan
- [ ] Anonymous pull still works
- [ ] Unauthenticated push fails (401)
- [ ] CI container builds pass with new auth and tagging
- [ ] `mise run services-check` passes

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

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/231

containers/kiwix-serve/Dockerfile

@@ -1,10 +1,13 @@
 # kiwix-serve container
 # Downloads pre-built binary from kiwix mirror
 
+ARG CONTAINER_APP_VERSION=3.8.1
+
 FROM alpine:3.22
 
 ARG TARGETPLATFORM
-ARG KIWIX_VERSION=3.8.1
+ARG CONTAINER_APP_VERSION
+ARG KIWIX_VERSION=${CONTAINER_APP_VERSION}
 
 RUN set -e && \
     apk --no-cache add dumb-init curl && \