fix(docs): replace broken enterprise link with sales contact (#13)

The '../../../enterprise/' relative link pointed to a non-existent
folder. Replaced with mailto:sales@capisc.io as a contact point for
enterprise deployment documentation.

Discovered during documentation audit.

Author: beonde

docs/reference/server/deployment.md

@@ -329,4 +329,4 @@ error: signature verification failed
 
 - [API Reference](api.md) — Full API documentation
 - [Badge CA](badge-ca.md) — CA operations
-- [Enterprise Deployment](../../../enterprise/) — Air-gapped and on-prem guides
+- [Contact Sales](mailto:sales@capisc.io) — Enterprise deployment options (air-gapped, on-prem)