Fix mirror org refs in ArgoCD apps and widen credential template (#266)

## Summary

- Widen `repo-creds-forge` URL prefix from `/eblume/` to host-wide `/` so it matches repos in all forge orgs (fixes `mirrors/` repos not getting SSH credentials)
- Update 8 ArgoCD app definitions from `eblume/<mirror>` → `mirrors/<mirror>` (immich-charts, cloudnative-pg-charts, external-secrets, connect-helm-charts)
- Fix stale alloy clone comment in Ansible defaults
- Bump immich v2.5.2 → v2.5.6 (bug-fix patches only)
- Update ArgoCD README bootstrap command and credential docs

## Context

Mirrors were migrated from `forge.ops.eblu.me/eblume/` to `forge.ops.eblu.me/mirrors/` in commit `cd57814`. Container Dockerfiles and image tags were updated, but ArgoCD app definitions and the repo credential template were missed, causing `ComparisonError` on apps that source Helm charts from mirrored repos.

## Deployment

1. Sync the ArgoCD `argocd` app first (picks up the widened credential template)
2. Sync the `apps` app (picks up new repo URLs for all 8 apps)
3. Verify immich resolves its ComparisonError: `argocd app get immich`
4. Sync immich to deploy v2.5.6: `argocd app sync immich`
5. Spot-check: `argocd app get external-secrets`, `argocd app get cloudnative-pg`, `argocd app get 1password-connect`

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/266

argocd/apps/external-secrets-crds-ringtail.yaml

@@ -11,7 +11,7 @@ metadata:
 spec:
   project: default
   source:
-    repoURL: ssh://forgejo@forge.ops.eblu.me:2222/eblume/external-secrets.git
+    repoURL: ssh://forgejo@forge.ops.eblu.me:2222/mirrors/external-secrets.git
     targetRevision: helm-chart-2.0.0
     path: config/crds/bases
     directory: