Expose timesync error in MQTT and web UI

BACKWARD-INCOMPATIBLE: MQTT faults payload now always includes err_last/err_last_text and err_last_age (schema change).

src/web_server.cpp

@@ -59,6 +59,21 @@ static bool auth_required() {
   return g_is_ap ? WEB_AUTH_REQUIRE_AP : WEB_AUTH_REQUIRE_STA;
 }
 
+static const char *fault_text(FaultType fault) {
+  switch (fault) {
+    case FaultType::MeterRead:
+      return "meter";
+    case FaultType::Decode:
+      return "decode";
+    case FaultType::LoraTx:
+      return "loratx";
+    case FaultType::TimeSync:
+      return "timesync";
+    default:
+      return "none";
+  }
+}
+
 static bool ensure_auth() {
   if (!auth_required()) {
     return true;
@@ -97,6 +112,7 @@ static String format_faults(uint8_t idx) {
   s += String(g_sender_faults[idx].lora_tx_fail);
   s += " last:";
   s += String(static_cast<uint8_t>(g_sender_last_errors[idx]));
+  s += " (" + String(fault_text(g_sender_last_errors[idx])) + ")";
   return s;
 }
 
@@ -335,6 +351,7 @@ static String render_sender_block(const SenderStatus &status) {
   if (status.has_data) {
     s += " err_tx:" + String(status.last_data.err_lora_tx);
     s += " err_last:" + String(static_cast<uint8_t>(status.last_data.last_error));
+    s += " (" + String(fault_text(status.last_data.last_error)) + ")";
   }
   s += format_faults(idx);
   s += "<br>";
@@ -588,7 +605,7 @@ static void handle_sender() {
           html += "<td>" + String(d.link_rssi_dbm) + "</td>";
           html += "<td>" + String(d.link_snr_db, 1) + "</td>";
           html += "<td>" + String(d.err_lora_tx) + "</td>";
-          html += "<td>" + String(static_cast<uint8_t>(d.last_error)) + "</td>";
+          html += "<td>" + String(static_cast<uint8_t>(d.last_error)) + " (" + String(fault_text(d.last_error)) + ")</td>";
           html += "</tr>";
         }
         html += "</table>";