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>

README.md

@@ -418,22 +418,17 @@ That manual is for a related model/revision, so use it as behavioral reference r
 
 ## TODO / worthwhile additions
 
-For this lamp, the most worthwhile additions are:
+Done: alarm data for all 4 alarms, Alarm 2 settings, sunset settings, ambient colour, snooze controls, grouped web UI, Home Assistant API, Home Assistant as a local time source, next/previous station, and diagnostics including versions and MCU link status.
+
+Still open:
 
-- **Finish DP127 decoding:** weekday-bit order and unknown bytes 4, 8 and 11.
-- **Find Alarm 2 extended settings:** sound, volume, wake-light level and sunrise duration are stored somewhere other than the DP127 middle block on this unit.
-- **Fully decode DP128:** make sunset/sleep duration, brightness, sound/radio choice and volume writable.
-- **Decode DP107:** turn the raw FM payload into actual frequency/preset information and add previous/next/scan controls; verify DP126.
-- **Ambient/color lamp control:** verify DP132 on this revision and expose color/effect controls rather than only DP129 power.
-- **Snooze:** verify DP116/117/130 from the exact-PID definition and expose them safely.
-- **Better local web UI:** move to Web Server v3 and group Light / Clock / Alarm 1 / Alarm 2 / Radio / Sunset / Diagnostics.
-- **Fully autonomous schedules:** add software-only extra alarms or weekday schedules without depending on Tuya cloud/app limits.
-- **Better clock correction:** configurable local NTP server, LAN-only synchronization, and optional drift measurement/correction.
-- **Astronomical sunrise/sunset:** use ESPHome's local sun calculations for real dusk/dawn behavior.
-- **Home Assistant native API:** optional `api:` support while retaining the standalone web UI.
-- **Diagnostics:** Wi-Fi RSSI, uptime, reboot reason, ESPHome/LibreTiny version, Tuya-link state and raw-packet viewer.
-- **Identify IC1:** obtain a board with readable top marking or otherwise identify the main appliance MCU.
 - **Upstream the UART fix:** replace the local PA13/PA14 workaround when ESPHome gains proper LibreTiny alternate-UART pin mapping.
+- **Astronomical sunrise/sunset:** use ESPHome's local sun calculations for real dusk/dawn behavior.
+- **Clock drift:** optional drift measurement and correction.
+- **Fully autonomous schedules:** software-only alarms, if 4 hardware alarms ever aren't enough.
+- **Identify IC1:** obtain a board with readable top marking or otherwise identify the main appliance MCU.
+
+FM frequency isn't available: DP107 only holds the station count and current station number.
 
 ## Safety / recovery notes