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.

base/matrix/kustomization.yaml

@@ -11,3 +11,5 @@ resources:
   - tuwunel-pvc.yaml
   - vault-secrets.yaml
   - hydra-oauth2client.yaml
+  - sol-deployment.yaml
+  - sol-config.yaml