Fixes pentest issue DG25-16 from 2025-09-02 (#159)

* sanitize user agent to prevent html injection
* add tests

Author: j-chmielewski

Cargo.lock

@@ -51,6 +51,7 @@ mime_guess = "2.0"
 base64 = "0.22"
 tower = "0.5"
 futures-util = "0.3"
+ammonia = "4.1.1"
 
 [build-dependencies]
 tonic-prost-build = "0.14"