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/config.h

@@ -105,7 +105,7 @@ const uint32_t SETUP_AP_DELAY = 20000;        // open the AP when WiFi fails thi
 const uint32_t WIFI_CONNECT_TIMEOUT = 30000;
 const uint32_t WIFI_RESTART_TIME = 10UL * 60 * 1000;
 
-#define FIRMWARE_VERSION "2.6.0"
+#define FIRMWARE_VERSION "2.7.0"
 
 // Home Assistant device id (do not change: Home Assistant's entities are linked to it)
 const uint8_t HA_DEVICE_ID[] = {0x34, 0x86, 0x5d, 0x3a, 0x08, 0x28};