Add local time source, station buttons and link status

Prefer Home Assistant time with public NTP as fallback. Add next and previous
station, ESPHome and LibreTiny versions, and an MCU link sensor. Update notes
with the raw capture results and tidy the README to-do list.

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

CLAUDE.md

@@ -57,7 +57,7 @@ From Tuya's definition for a sibling product (tuya-local issue #3821). See the R
 - DP127 writes are ignored while an alarm is snoozed.
 - A mode without light sets brightness to 0, and a light mode with brightness 0 falls back to no light, so the firmware sets a level when choosing a light mode.
 - Alarm radio stations were reset to 1 while no stations were saved.
-- Radio Volume writes were rejected with the radio off.
+- Radio Volume and station writes are ignored with the radio off. With it on, both work, and the station stays selected after turning it off.
 - Keep `default_transition_length` at 0. A transition sends about 50 MCU writes a second.
 - LibreTiny before v1.14.0 can hang after a software restart or OTA until powered off for about 30 seconds (LibreTiny issue #396). The config pins v1.14.0. Drop the pin once ESPHome defaults to it or newer.
 - "Last Restart Reason" reports Power-On even after software restarts.
@@ -69,9 +69,12 @@ Verified:
 - Wednesday-only rang on a Wednesday, which fits bit 0 = Monday. A Tuesday-only silent test was skipped.
 - Sunset starts and stops. Its sound was heard, and a glow was seen but not clearly caused by it.
 - A manual scan found 2 stations, while a scan started from the firmware found 0.
+- Next/Previous Station and Radio Station change the MCU's station, with wrap-around. Audio on them wasn't confirmed: the owner heard no radio signal.
+- Home Assistant is used as the time source when connected, with public NTP as the fallback.
 
 Not tested:
-- Radio alarms, Radio Station changes and Radio Volume with the radio on.
+- Radio alarms.
+- Running without internet, or without Home Assistant.
 - Bedtime Fade and double knock on the real light.
 - Whether Ambient Color and Snooze Action labels match what the lamp does.