feat(infra): add K3s GitOps infrastructure and Packer golden image build (#25)

### Summary of Changes

This PR introduces a declarative, GitOps-managed cloud infrastructure
for the monorepo using K3s, Flux v2, and HashiCorp Packer:

1. **Packer Golden Image Builder (`ci/packer/`)**:
- Automated Debian 12 minimal base OS image creation using QEMU builder,
UEFI firmware, GPT partition scheme, and 2M cluster size `.qcow2`
conversion.
- Cloud-init, `virtio` kernel drivers, and serial console (`ttyS0`,
115200 baud).
- Pre-installed K3s binary (`v1.31.2+k3s1`) with isolated first-boot
token and cert generation.
   - Full identity sanitization (`machine-id` and SSH host key resets).

2. **First-Boot Cloud-Init Bootstrapping
(`ci/cloud-init/user-data.yaml`)**:
- Configures K3s with `servicelb` disabled and TLS SANs for custom
domains and static IP.
- Waits for API readiness, initializes `flux-system` namespace, injects
`sops-age` secret, and triggers Flux sync.

3. **SOPS & GitOps Root Orchestration (`.sops.yaml`,
`ci/k8s/clusters/production/`)**:
- SOPS encryption configuration targeting Kubernetes secrets with `age`
key recipient.
- Flux v2 `GitRepository` and `Kustomization` manifests tracking `next`.

4. **Infrastructure & Networking (`ci/k8s/base/`,
`ci/k8s/infrastructure/`)**:
   - Dedicated `com-ermnvldmr` namespace.
- `cert-manager` HTTP-01 `ClusterIssuer` (`letsencrypt-prod` &
`letsencrypt-staging`).
- Traefik Ingress routing for `ermnvldmr.com`, `www.ermnvldmr.com`,
`docs.ermnvldmr.com`, and `analytics.ermnvldmr.com`.

5. **PostgreSQL & Applications (`ci/k8s/apps/`)**:
- PostgreSQL 16 StatefulSet on 5Gi `local-path` persistent storage with
low-memory tuning.
- Deployments for `www` (pinned `sha-6d33b71`), `docs` (pinned
`sha-91f5245`), and `umami` (pinned `postgresql-v2.14.0`) with
zero-downtime rolling update strategy.

6. **CI/CD Workflows (`.github/workflows/`)**:
- `ci - next/build-golden-image`: Workflow to build and upload
`com-ermnvldmr-debian-12-k3s-amd64-<tag>.qcow2` to static S3
`/dev/images/`.
- Updated `services-www-releases-dispatch-release.yml` and
`services-docs-next-required.yml` with GitOps deployment steps.

ci/k8s/apps/umami/kustomization.yaml

@@ -0,0 +1,11 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: com-ermnvldmr
+resources:
+  - configmap.yaml
+  - secret.template.yaml
+  - deployment.yaml
+  - service.yaml
+images:
+  - name: ghcr.io/umami-software/umami
+    newTag: postgresql-v2.14.0