Initial implementation: aptly container image, Compose stacks, Helm chart, and Gitea Actions pipelines

Provides a self-contained, containerized aptly (Debian repo manager)
stack with independently releasable image and Helm chart versions.

- images/: aptly-server (aptly built from source, cross-compiled) and
  aptly-deb-builder (nfpm + dpkg-buildpackage) container images
- rootfs/: shared aptly-init/aptly-reconcile/aptly-push/aptly-pack
  scripts consumed identically by Compose and the Helm chart, driven
  by one declarative state.yaml contract
- compose/: test (ephemeral, open) and production docker-compose
  stacks with an nginx read/auth sidecar
- charts/aptly/: aptly-native Helm chart covering every security
  posture from fully open to authenticated read+write, Ingress and
  Gateway API support (usable in parallel for migration scenarios),
  metrics, and declarative repo/mirror/publish reconciliation via a
  Helm hook
- .gitea/workflows/: CI (lint, template, kubeconform, E2E smoke test)
  plus separately tagged image (image/v*) and chart (chart/v*)
  releases, weekly rebuilds, and a preflight workflow validating the
  runner's Docker/Helm-OCI capabilities
- pubkeys/: RSA chart-signing key for Helm --sign / Artifact Hub's
  signKey annotation (Helm can't verify Ed25519 keys)
- docs/, README.md, charts/aptly/README.md: usage, security, and
  versioning documentation

charts/aptly/templates/poddisruptionbudget.yaml

@@ -0,0 +1,16 @@
+{{- if .Values.podDisruptionBudget.enabled }}
+apiVersion: policy/v1
+kind: PodDisruptionBudget
+metadata:
+  name: {{ include "aptly.fullname" . }}
+  labels:
+    {{- include "aptly.labels" . | nindent 4 }}
+spec:
+  # With replicas fixed at 1 (see templates/statefulset.yaml), a
+  # minAvailable:1 budget would block every voluntary node drain forever —
+  # maxUnavailable is the only sane knob here.
+  maxUnavailable: {{ .Values.podDisruptionBudget.maxUnavailable }}
+  selector:
+    matchLabels:
+      {{- include "aptly.selectorLabels" . | nindent 6 }}
+{{- end }}