joystick UI:

- track real RTC sync source on the joystick Time screen
- gate joystick-only UI helpers behind stub headers so non-joystick builds skip the extra code without #ifdef at every call site.

zephcore/app/main_observer.cpp

@@ -17,7 +17,6 @@
 #include <zephyr/kernel.h>
 #include <zephyr/drivers/uart.h>
 #include <zephyr/sys/ring_buffer.h>
-#include <helpers/time_sync.h>
 
 #define CLI_REPLY_SIZE 256
 
@@ -222,7 +221,6 @@ static mesh::ZephyrRTCClock s_rtc_clock;
 static void time_sync_cb(uint32_t unix_ts)
 {
 	s_rtc_clock.setCurrentTime(unix_ts);
-	time_sync_report(TIME_SYNC_WIFI);
 	LOG_INF("RTC synced from SNTP: %u", unix_ts);
 }