refactor(couchdb): move raw manifests to templates/ subdir

Per Tony's recommendation — eliminates the explicit include filter.
New manifests go in templates/ and are picked up automatically by ArgoCD.
No filter to update when adding future resources.

Moved: namespace.yaml, externalsecret.yaml, ingress-public.yaml -> templates/

cluster/applications/couchdb/templates/namespace.yaml

@@ -0,0 +1,7 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: couchdb
+  labels:
+    app.kubernetes.io/name: couchdb
+    app.kubernetes.io/part-of: mk-labs