Add conversions for Home Assistant values: duration, time, own texts, auto unit

- Show as number (multiplier, decimals, auto unit W -> kW -> MW, without
  minus sign), duration (seconds/minutes/hours as 2h 21m, 2:21:00, 2:21 or
  smart), time (HA timestamps in local time, with weekday or date, or
  relative: over 34 min / 12 min geleden) or own texts per state.
- Page format 3; version 2 pages are converted. Version 2.7.0.

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

src/esp32/logic/local_time.h

@@ -11,4 +11,5 @@ struct LocalTime
 	int minute = 0;
 	int second = 0;
 	int millisecond = 0;
+	int utc_offset = 0; // minutes: local time - UTC (for Home Assistant timestamps)
 };