fix(docs/deploy): harden public docs deployment and pin images

Add a pod-level security context to the nginx container in the public
docs deployment (non-root uid 101, dropped capabilities, read-only
root filesystem, RuntimeDefault seccomp) and rebind it to unprivileged
port 8080 so it does not need CAP_NET_BIND_SERVICE. The nginx PID and
proxy temp paths move under a tmpfs-backed emptyDir so the read-only
root filesystem does not break startup.

Replace the mutable :main tags on both containers with immutable
sha256 digests and switch imagePullPolicy to IfNotPresent so each
rollout references an auditable artifact instead of whatever happens
to be tagged :main when the pod starts. The docs-deploy workflow now
overlays the freshly built docs digest via `kustomize edit set image`
so the manifest stays accurate without a manual edit on each push to
main. The docs Dockerfile pins its node and nginx-micro base images
to specific versions for the same reason.

Ref: AWOO-011, AWOO-012
Assisted-by: Claude Opus 4.7 via Claude Code
Signed-off-by: Xe Iaso <me@xeiaso.net>

.github/actions/spelling/expect.txt

@@ -318,6 +318,7 @@ screenshots
 searchbot
 searx
 sebest
+seccomp
 secretplans
 selfsigned
 Semrush

.github/workflows/docs-deploy.yml

@@ -52,6 +52,15 @@ jobs:
           platforms: linux/amd64
           push: true
 
+      - name: Pin docs image to built digest
+        working-directory: docs/manifest
+        env:
+          DIGEST: ${{ steps.build.outputs.digest }}
+        run: |
+          KUSTOMIZE_VERSION=v5.4.3
+          curl -fsSL "https://github.com/kubernetes-sigs/kustomize/releases/download/kustomize/${KUSTOMIZE_VERSION}/kustomize_${KUSTOMIZE_VERSION}_linux_amd64.tar.gz" | tar -xz
+          ./kustomize edit set image "ghcr.io/techarohq/anubis/docs=ghcr.io/techarohq/anubis/docs@${DIGEST}"
+
       - name: Apply k8s manifests to limsa lominsa
         uses: actions-hub/kubectl@934aaa4354bbbc3d2176ae8d7cae92d515032dff # v1.35.3
         env: