[web_server] Simplify datetime formatting with buf_append_printf

esphome/components/web_server/web_server.cpp

@@ -1178,11 +1178,7 @@ std::string WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_co
 
   // Format: YYYY-MM-DD (max 10 chars + null)
   char value[12];
-#ifdef USE_ESP8266
-  snprintf_P(value, sizeof(value), PSTR("%d-%02d-%02d"), obj->year, obj->month, obj->day);
-#else
-  snprintf(value, sizeof(value), "%d-%02d-%02d", obj->year, obj->month, obj->day);
-#endif
+  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d", obj->year, obj->month, obj->day);
   set_json_icon_state_value(root, obj, "date", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1241,11 +1237,7 @@ std::string WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_co
 
   // Format: HH:MM:SS (8 chars + null)
   char value[12];
-#ifdef USE_ESP8266
-  snprintf_P(value, sizeof(value), PSTR("%02d:%02d:%02d"), obj->hour, obj->minute, obj->second);
-#else
-  snprintf(value, sizeof(value), "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
-#endif
+  buf_append_printf(value, sizeof(value), 0, "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
   set_json_icon_state_value(root, obj, "time", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1304,13 +1296,8 @@ std::string WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail
 
   // Format: YYYY-MM-DD HH:MM:SS (max 19 chars + null)
   char value[24];
-#ifdef USE_ESP8266
-  snprintf_P(value, sizeof(value), PSTR("%d-%02d-%02d %02d:%02d:%02d"), obj->year, obj->month, obj->day, obj->hour,
-             obj->minute, obj->second);
-#else
-  snprintf(value, sizeof(value), "%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour, obj->minute,
-           obj->second);
-#endif
+  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour,
+                    obj->minute, obj->second);
   set_json_icon_state_value(root, obj, "datetime", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);