logging: deploy logviewer v0.1.0 behind oauth2-proxy

The logviewer UI gives browser access to the ClickHouse log store; it is
deployed behind an Authentik-gated oauth2-proxy front so only
akP-logviewer-admin members reach it, at https://logviewer.unkin.net.

- Adds the logviewer Deployment (docker-internal/logviewer:v0.1.0) reading
  ClickHouse via the existing clickhouse-logreader credentials
- Adds an oauth2-proxy front (quay.io v7.15.3) with ak_groups-based
  authorization, mirroring the arrstack pattern
- Syncs kv kubernetes/namespace/logging/default/oauth-credentials into the
  logviewer-oauth-credentials Secret via the existing default VaultAuth
- Adds internal Gateway + HTTPRoutes for logviewer.unkin.net (vault-issuer
  cert, external-dns -> 198.18.200.4, http->https redirect)
- Registers the logviewer directory in the logging kustomization

apps/base/logging/logviewer/httproute.yaml

@@ -0,0 +1,49 @@
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: logviewer-http-redirect
+  namespace: logging
+spec:
+  hostnames:
+    - logviewer.unkin.net
+  parentRefs:
+    - group: gateway.networking.k8s.io
+      kind: Gateway
+      name: logviewer
+      sectionName: http
+  rules:
+    - filters:
+        - type: RequestRedirect
+          requestRedirect:
+            scheme: https
+            statusCode: 301
+      matches:
+        - path:
+            type: PathPrefix
+            value: /
+---
+apiVersion: gateway.networking.k8s.io/v1
+kind: HTTPRoute
+metadata:
+  name: logviewer
+  namespace: logging
+spec:
+  hostnames:
+    - logviewer.unkin.net
+  parentRefs:
+    - group: gateway.networking.k8s.io
+      kind: Gateway
+      name: logviewer
+      sectionName: https
+  rules:
+    - backendRefs:
+        - group: ""
+          kind: Service
+          name: logviewer-oauth2
+          port: 80
+          weight: 1
+      matches:
+        - path:
+            type: PathPrefix
+            value: /