fix: extract auth config to ConfigMap + SOPS secret, update slug to poimen

- Add k8s/app/config.yaml (ConfigMap) for non-sensitive env vars
- Add k8s/app/auth.enc.yaml (SOPS-encrypted) for AUTHENTIK_ISSUER, AUDIENCE
- Add k8s/app/secret-generator.yaml (KSOPS generator for ArgoCD)
- Deployment uses envFrom instead of inline env vars
- Update Authentik slug from poimen-memory to poimen (404 on OIDC discovery)
- Update OpenSearch JWKS/issuer URLs to match new slug
- Reloader (auto-reload-all=true) triggers rollout on config change

k8s/app/kustomization.yaml

@@ -5,6 +5,9 @@ resources:
   # vault-pvc.yaml removed — memory service uses pgvector, not local storage
   - deployment.yaml
   - service.yaml
+  - config.yaml
   - obsidian.yaml
-  # Secret managed separately (SealedSecret in homelab)
+  # Legacy secret managed separately
   # - secrets.yaml
+generators:
+  - secret-generator.yaml