PTP: hardware timestamping is not a setting any more

The hw_ts config key was never read (hardware timestamps are always used);
the checkbox suggested it could be turned off. Removed from the config,
the page and the docs; status.ptp.hw_ts still reports it.

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

components/aes67_ptp/aes67_ptp.c

@@ -9,7 +9,7 @@
 static const char PTP_DEFAULTS[] =
     "{\"mode\":\"multicast\",\"role\":\"auto\",\"domain\":0,\"priority1\":250,\"priority2\":250,"
     "\"log_sync\":0,\"log_announce\":1,\"announce_timeout\":3,\"log_delay_req\":0,"
-    "\"dscp\":46,\"hw_ts\":true}";
+    "\"dscp\":46}";     // hardware timestamps always (status.ptp.hw_ts)
 
 static bool ptp_validate(const cJSON *g, char *err, size_t n)
 {