feat(matrix): add Sol virtual librarian deployment manifests

Sol is a Matrix bot with E2EE that archives conversations to OpenSearch
and responds via Mistral AI function calling. Adds deployment, PVC,
ConfigMap (sol.toml + system prompt), VaultStaticSecret for credentials,
and production overlay image entry.

overlays/production/kustomization.yaml

@@ -85,6 +85,11 @@ images:
     newName: src.DOMAIN_SUFFIX/studio/tuwunel
     newTag: latest
 
+  # Sol virtual librarian — built and pushed by `sunbeam build sol`
+  - name: sol
+    newName: src.DOMAIN_SUFFIX/studio/sol
+    newTag: latest
+
 patches:
   # Pingora host ports — bind :80/:443 to the host network
   - path: patch-pingora-hostport.yaml