feat(dyndns): add get_ddns_status() for os-ddclient enabled/running state

Verified against a live OPNsense 24.7 instance: the service id is
"ddclient" but the REST module is "dyndns" (/api/ddclient/* all 404).
Scoped to enabled/running only -- no ddclient/dyndns account was
configured on the test device to verify a per-account "registered IP"
shape against, so that comparison is deliberately left out rather than
guessed.

napalm_opnsense/opnsense.py

@@ -1091,6 +1091,33 @@ class OPNsenseDriver(FirewallDriver):
             })
         return result
 
+    def get_ddns_status(self) -> dict[str, Any] | None:
+        """Return Dynamic DNS (os-ddclient) enabled/running state.
+
+        Calls ``GET /api/dyndns/service/status`` and
+        ``GET /api/dyndns/settings/get`` -- note the API module is
+        "dyndns", not "ddclient" (the service id reported by
+        get_services() is "ddclient", but its REST controller lives under
+        a different, historical module name).
+
+        Returns ``{"enabled": bool, "running": bool}``, or ``None`` if the
+        plugin isn't installed/reachable. Scoped to enabled/running only:
+        no per-account "registered IP" comparison, since that would need a
+        configured account to verify the response shape against.
+        """
+        try:
+            status = self._get("/api/dyndns/service/status")
+            settings = self._get("/api/dyndns/settings/get")
+        except Exception as exc:
+            logger.warning("get_ddns_status() failed: %s", exc)
+            return None
+
+        general = settings.get("ddclient", {}).get("general", {})
+        return {
+            "enabled": general.get("enabled") == "1",
+            "running": status.get("status") == "running",
+        }
+
     def get_dhcp_leases(self) -> list[dict[str, Any]]:
         """Return active DHCP leases from OPNsense.