fix(server): ignore datagrams that are not named HTB/PLG messages

A scanner's SIP INVITE on the public UDP port was parsed as a message without
a name and signed on a host called "unknown". Non-client datagrams are still
journaled but no longer create hosts or get an ACK.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

hbd/server/udp.py

@@ -422,6 +422,12 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
         except Exception as e:
             logger.debug(f"Failed to log message to journal: {e}")
     
+    # Only named HTB/PLG datagrams come from clients; anything else (e.g. an internet scanner's
+    # SIP probe) is journaled above but must not sign on a host.
+    if msg.get("ID") not in ("HTB", "PLG") or not msg.get("name"):
+        logger.debug("Ignoring non-client datagram from %s", addr)
+        return
+
     cfg = ctx.get("config", {})
     hbdcls = ctx.get("hbdclass")
     msg_to_websockets = ctx.get("msg_to_websockets")
@@ -430,7 +436,7 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
 
     # normalize addr (ip, port)
     ip = addr[0] if isinstance(addr, (list, tuple)) else addr
-    name = msg.get("name", "unknown")
+    name = msg["name"]
     from ..common.utils import shortname
     from . import config as config_mod