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/miniflux/Dockerfile

@@ -1,7 +1,8 @@
 # Miniflux RSS feed reader
 # Based on upstream packaging/docker/alpine/Dockerfile
 
-ARG MINIFLUX_VERSION=2.2.17
+ARG CONTAINER_APP_VERSION=2.2.17
+ARG MINIFLUX_VERSION=${CONTAINER_APP_VERSION}
 
 FROM golang:alpine3.22 AS build