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/kustomization.yaml

@@ -15,6 +15,7 @@ resources:
   - serviceaccount_logarchiver.yaml
   - configmap_logarchiver.yaml
   - deployment_logarchiver.yaml
+  - logviewer
 
 # Vector pipelines are the single source of truth (also validated by
 # `vector test` in CI). Mounted into each tier via `existingConfigMaps`.