C1: deploy adelaide-baby-shower-app to ringtail k3s

Adds the Adelaide / Heidi / Addie baby shower app — a Django guest
splash, raffle picker, and prize-assignment console — on ringtail k3s.
Public landing at shower.eblu.me (via fly proxy), tailnet admin at
shower.ops.eblu.me. App source: forge.eblu.me/eblume/adelaide-baby-shower-app,
wheel-published to the Forgejo Packages PyPI index.

Manifests under argocd/manifests/shower/: NFS-backed PVC for /app/media,
local-path PVC for SQLite, ExternalSecret pulling DJANGO_SECRET_KEY from
1Password (item "Shower (blumeops)"), Tailscale ProxyGroup ingress.

Defense-in-depth for the public surface:
  - /admin/ blocked at the fly edge except /admin/login/ and /admin/logout/
  - shower_auth rate limit on the login path
  - new fail2ban filter+jail with a per-service shower-deny.conf
    (nginx-deny action generalized to accept nginx_deny_file)
  - django-axes (5 / 1h) keyed on (username, ip_address)

Plus: Caddy route on indri, Pulumi gandi CNAME, Grafana APM dashboard
mirroring docs-apm.json, runbook at how-to/operations/shower-app.md,
and a service-versions entry. X-Clacks-Overhead set on the new server
block — GNU Terry Pratchett.

Build: containers/shower/default.nix uses dockerTools to ship a
nixpkgs Python plus a startup wrapper that installs the wheel into
/app/data/.venv on first boot and execs gunicorn. Lets the wheel come
from forge PyPI without pinning hashes for every transitive dep.

Prerequisites tracked in the runbook (not yet executed):
  - NFS share sifaka:/volume1/shower (manual Synology step)
  - 1Password item "Shower (blumeops)" with secret-key field
  - container build via `mise run container-build-and-release shower`
  - Pulumi dns-up after merge
  - fly certs add shower.eblu.me

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

argocd/manifests/shower/kustomization.yaml

@@ -0,0 +1,17 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: shower
+
+resources:
+  - configmap.yaml
+  - external-secret.yaml
+  - pv-nfs.yaml
+  - pvc.yaml
+  - service.yaml
+  - ingress-tailscale.yaml
+  - deployment.yaml
+
+images:
+  - name: registry.ops.eblu.me/blumeops/shower
+    newTag: v1.0.0-PLACEHOLDER-nix