Display drifitng stats

lib/hal/HalClock.cpp

@@ -227,6 +227,8 @@ bool isSynced() {
 
 bool isApproximate() { return clockApproximate; }
 
+time_t lastSyncTime() { return nvsReadSyncTime(); }
+
 void formatTime(char* buf, size_t bufSize, bool use24h) {
   if (!isSynced()) {
     snprintf(buf, bufSize, "--:--");

lib/hal/HalClock.h

@@ -55,6 +55,10 @@ bool isSynced();
 /// may have drifted.  Cleared on NTP sync.
 bool isApproximate();
 
+/// Returns the epoch of the last successful NTP sync (from NVS), or 0 if
+/// no sync has ever been recorded.
+time_t lastSyncTime();
+
 /// Format the current time for display.  Returns "--:--" if the clock was
 /// never synced, prefixes with "~" if approximate.
 /// When use24h is false, formats as "2:05pm" / "12:30am".