fixes and improvements

backend/src/media_library_viewer_api/services/known_hosts.py

@@ -41,6 +41,16 @@ def _fetch_server_key(host: str, port: int, timeout: int = 30) -> paramiko.PKey:
         sock.close()
 
 
+def has_known_host(host: str, port: int, known_hosts_path: Path) -> bool:
+    """Return whether the given host/port is already present in known_hosts."""
+    if not host or not known_hosts_path.exists():
+        return False
+    host_alias = _host_alias(host, port)
+    host_keys = paramiko.HostKeys()
+    host_keys.load(str(known_hosts_path))
+    return host_keys.lookup(host_alias) is not None
+
+
 def ensure_known_host(host: str, port: int, known_hosts_path: Path, *, strict: bool = True) -> bool:
     """Ensure a host key entry exists for the given host/port.