Add k3s, 1Password Connect, and systemd nix-container-builder to ringtail (#209)

## Summary

  Extends ringtail from a desktop/gaming NixOS box into an infrastructure node with a k3s cluster, secrets management, and a Forgejo Actions
  runner for building containers with Nix.

  ### K3s cluster
  - Single-node k3s with Traefik/ServiceLB/metrics-server disabled (minimal footprint)
  - TLS SAN set to `ringtail.tail8d86e.ts.net` so ArgoCD on indri can manage it via Tailscale
  - Containerd registry mirrors pull through Zot on indri (`k3s-registries.yaml`)
  - Tailscale interface added to `trustedInterfaces` for cross-node ArgoCD access
  - `kubectl` added to system packages

  ### 1Password Connect + External Secrets Operator
  - Four new ArgoCD apps targeting `k3s-ringtail`: `1password-connect-ringtail`, `external-secrets-crds-ringtail`, `external-secrets-ringtail`,
  `external-secrets-config-ringtail`
  - Reuses the same Helm charts/values as indri, just pointed at ringtail's k3s API server
  - Bootstrap secrets (`op-credentials`, `onepassword-token`) provisioned by Ansible pre_tasks via `op read`, then applied to the `1password`
  namespace in post_tasks

  ### Systemd Forgejo Actions runner
  - Native `services.gitea-actions-runner` with `forgejo-runner` package — no DinD, no k8s pod, runs directly on the NixOS host
  - Label `nix-container-builder:host` — jobs execute on the host with `nix`, `skopeo`, `nodejs`, etc. in PATH
  - Registration token fetched from 1Password (`Forgejo Secrets/runner_reg`) by Ansible and written to `/etc/forgejo-runner/token.env`
  - Runner's dynamic user (`gitea-runner`) added to `nix.settings.trusted-users` for nix daemon access

  ### Nix container build workflow
  - New `.forgejo/workflows/build-container-nix.yaml` triggers on `*-nix-v[0-9]*` tags (e.g. `nettest-nix-v1.0.0`)
  - Builds with `nix build -f containers/<name>/default.nix`, pushes to Zot via `skopeo copy`
  - Existing Dockerfile workflow guarded with `if: !contains(github.ref_name, '-nix-v')` to avoid double-triggering

  ### Mise task updates
  - `container-tag-and-release` auto-detects `default.nix` vs `Dockerfile` and uses the appropriate tag format (`-nix-v` vs `-v`)
  - `container-list` shows build type indicator (`[nix]` / `[dockerfile]`)

  ## Post-merge

  1. `mise run provision-ringtail` — deploys k3s token, runner token, NixOS rebuild
  2. Register k3s cluster in ArgoCD (first time only):
     ```fish
     ssh ringtail 'sudo cat /etc/rancher/k3s/k3s.yaml' | \
       sed 's|127.0.0.1|ringtail.tail8d86e.ts.net|' > /tmp/k3s-ringtail.yaml
     set -x KUBECONFIG /tmp/k3s-ringtail.yaml
     argocd cluster add default --name k3s-ringtail
  3. Sync ArgoCD apps in order: 1password-connect-ringtail -> external-secrets-crds-ringtail -> external-secrets-ringtail ->
  external-secrets-config-ringtail
  4. Verify runner: ssh ringtail 'systemctl status gitea-runner-nix-container-builder'
  5. Check Forgejo admin panel for ringtail-nix-builder runner online
  6. Test: create containers/<name>/default.nix, tag with <name>-nix-v0.1.0

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/209

.forgejo/workflows/build-container-nix.yaml

@@ -0,0 +1,89 @@
+# Nix container build workflow
+# Triggers on tags matching: <container>-nix-v<version>
+# Builds from containers/<container>/default.nix using nix build
+# Pushes to Zot registry via skopeo
+#
+# Examples:
+#   nettest-nix-v1.0.0  -> builds containers/nettest/default.nix
+#   myapp-nix-v2.1.0    -> builds containers/myapp/default.nix
+name: Build Container (Nix)
+
+on:
+  push:
+    tags:
+      - '*-nix-v[0-9]*'
+
+jobs:
+  build:
+    runs-on: nix-container-builder
+    steps:
+      - name: Parse tag
+        id: parse
+        run: |
+          TAG="${GITHUB_REF_NAME}"
+          echo "Tag: $TAG"
+
+          # Extract container name (everything before -nix-v)
+          # e.g., "nettest-nix-v1.0.0" -> "nettest"
+          CONTAINER="${TAG%-nix-v[0-9]*}"
+          VERSION="${TAG#"${CONTAINER}"-nix-}"
+
+          echo "container=$CONTAINER" >> "$GITHUB_OUTPUT"
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+          echo "Container: $CONTAINER"
+          echo "Version: $VERSION"
+
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Check if nix container exists
+        id: check
+        run: |
+          CONTAINER="${{ steps.parse.outputs.container }}"
+          CONTEXT="containers/$CONTAINER"
+
+          if [ -f "$CONTEXT/default.nix" ]; then
+            echo "Found $CONTEXT/default.nix"
+            echo "exists=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "No default.nix found at $CONTEXT/default.nix"
+            echo "exists=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Skip if container not found
+        if: steps.check.outputs.exists != 'true'
+        run: |
+          echo "========================================"
+          echo "Nix container not found: ${{ steps.parse.outputs.container }}"
+          echo "========================================"
+          echo ""
+          echo "Tag '${{ github.ref_name }}' does not match any nix container in containers/"
+          echo ""
+          echo "Available nix containers:"
+          for nix in containers/*/default.nix; do
+            [ -f "$nix" ] && echo "  - $(basename "$(dirname "$nix")")"
+          done
+          echo ""
+          echo "Skipping build."
+
+      - name: Build with nix
+        if: steps.check.outputs.exists == 'true'
+        id: build
+        run: |
+          CONTAINER="${{ steps.parse.outputs.container }}"
+          echo "Building containers/$CONTAINER/default.nix"
+          nix build -f "containers/$CONTAINER/default.nix" -o result
+          echo "Build complete: $(readlink result)"
+
+      - name: Push to registry
+        if: steps.check.outputs.exists == 'true'
+        run: |
+          CONTAINER="${{ steps.parse.outputs.container }}"
+          VERSION="${{ steps.parse.outputs.version }}"
+          IMAGE="registry.ops.eblu.me/blumeops/$CONTAINER:$VERSION"
+
+          echo "Pushing to $IMAGE"
+          skopeo copy \
+            "docker-archive:result" \
+            "docker://$IMAGE"
+          echo "Push complete: $IMAGE"

.forgejo/workflows/build-container.yaml

@@ -17,6 +17,7 @@ on:
 
 jobs:
   build:
+    if: "!contains(github.ref_name, '-nix-v')"
     runs-on: k8s
     steps:
       - name: Parse tag