feat(lotw): show last sync time on settings, precise incremental cursor

The stored sync cursor was 'yyyyMMdd', which LoTW's qso_qslsince silently
ignores (measured live: it falls back to the system-supplied default).
Write a full UTC 'yyyy-MM-dd HH:mm:ss' cursor instead — the documented
format LoTW honors — so incremental pulls are exact (second precision)
and the settings page can show the last successful sync time on the LoTW
card, formatted like the ephemeris update time (prefs_updated_title).
Legacy yyyyMMdd cursors are normalized for the API, the gate and the
display (lotwCursorApi/lotwCursorDate/lotwCursorEpochMs).

app/src/main/java/com/rtbishop/look4sat/MainApplication.kt

@@ -27,6 +27,7 @@ import com.rtbishop.look4sat.core.domain.repository.IMainContainer
 import com.rtbishop.look4sat.core.domain.repository.LoTWSyncMode
 import com.rtbishop.look4sat.core.domain.repository.LoTWResult
 import com.rtbishop.look4sat.core.domain.repository.applyLoTWGridResult
+import com.rtbishop.look4sat.core.domain.repository.lotwCursorApi
 import com.rtbishop.look4sat.core.domain.repository.lotwSyncToday
 import com.rtbishop.look4sat.core.domain.repository.resolveLoTWSyncMode
 import com.rtbishop.look4sat.core.domain.repository.shouldAutoSyncLoTW
@@ -110,7 +111,7 @@ class MainApplication : Application(), IContainerProvider {
         ) return
         val callsign = lotwSettings.callsign.trim().uppercase()
         val mode = resolveLoTWSyncMode(settingsRepo.getLastLotwSyncCallsign(), callsign, requested = null)
-        val since = if (mode == LoTWSyncMode.Incremental) settingsRepo.getLastLotwSyncDate() else ""
+        val since = if (mode == LoTWSyncMode.Incremental) lotwCursorApi(settingsRepo.getLastLotwSyncDate()) else ""
         println("Started periodic LoTW grid sync (${mode.name.lowercase()})")
         val result = container.lotwRepo.fetchConfirmedGridQsos(callsign, lotwSettings.password, since)
         if (result is LoTWResult.Success) {