feat(rtc): add loopRTC and appendTimeStatus hook

src/rtcsync.h

@@ -92,3 +92,40 @@ bool syncFromNTP() {
   lastNtpSyncEpoch = after;
   return true;
 }
+
+// Aus loop() aufgerufen. Triggert syncFromNTP():
+//  - bei steigender Flanke von WiFi.isConnected() (STA-Reconnect)
+//  - alle 24h, sobald STA verbunden ist
+// Reine Vergleichsoperationen, NTP-Roundtrip selbst ist blockierend (~ms..5s).
+void loopRTC() {
+  bool sta = (WiFi.status() == WL_CONNECTED);
+
+  // Edge: false -> true (frischer STA-Connect)
+  if (sta && !lastStaConnected) {
+    Serial.println("[RTC] STA-Reconnect erkannt — NTP-Sync");
+    syncFromNTP();
+  }
+  lastStaConnected = sta;
+
+  // 24h-Periodik (nur wenn STA online)
+  if (sta && ntpEverSynced) {
+    time_t nowEpoch = time(NULL);
+    if (nowEpoch - lastNtpSyncEpoch >= 86400) {
+      Serial.println("[RTC] 24h-Periodik — NTP-Sync");
+      syncFromNTP();
+    }
+  }
+}
+
+// Weak-Hook-Override aus timesync.h — erweitert /api/time um RTC-Status.
+extern "C" void appendTimeStatus(JsonDocument &doc) {
+  doc["rtc_available"] = rtcAvailable;
+  doc["rtc_synced_from_ntp"] = ntpEverSynced;
+  doc["last_ntp_sync_ago_s"] =
+      ntpEverSynced ? (long)(time(NULL) - lastNtpSyncEpoch) : (long)-1;
+  if (rtcAvailable) {
+    doc["rtc_time_utc"] = (long)rtc.now().unixtime();
+  } else {
+    doc["rtc_time_utc"] = (long)0;
+  }
+}