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/vault-secrets.yaml

@@ -37,3 +37,31 @@ spec:
           text: "{{ index .Secrets \"turn-secret\" }}"
         TUWUNEL_REGISTRATION_TOKEN:
           text: "{{ index .Secrets \"registration-token\" }}"
+---
+apiVersion: secrets.hashicorp.com/v1beta1
+kind: VaultStaticSecret
+metadata:
+  name: sol-secrets
+  namespace: matrix
+spec:
+  vaultAuthRef: vso-auth
+  mount: secret
+  type: kv-v2
+  path: sol
+  refreshAfter: 60s
+  rolloutRestartTargets:
+    - kind: Deployment
+      name: sol
+  destination:
+    name: sol-secrets
+    create: true
+    overwrite: true
+    transformation:
+      excludeRaw: true
+      templates:
+        matrix-access-token:
+          text: '{{ index .Secrets "matrix-access-token" }}'
+        matrix-device-id:
+          text: '{{ index .Secrets "matrix-device-id" }}'
+        mistral-api-key:
+          text: '{{ index .Secrets "mistral-api-key" }}'