[dashboard_import] Store package import URL in .rodata instead of RAM

esphome/components/dashboard_import/dashboard_import.cpp

@@ -3,10 +3,10 @@
 namespace esphome {
 namespace dashboard_import {
 
-static std::string g_package_import_url;  // NOLINT
+static const char *g_package_import_url = "";  // NOLINT
 
-const std::string &get_package_import_url() { return g_package_import_url; }
-void set_package_import_url(std::string url) { g_package_import_url = std::move(url); }
+const char *get_package_import_url() { return g_package_import_url; }
+void set_package_import_url(const char *url) { g_package_import_url = url; }
 
 }  // namespace dashboard_import
 }  // namespace esphome

esphome/components/dashboard_import/dashboard_import.h

@@ -1,12 +1,10 @@
 #pragma once
 
-#include <string>
-
 namespace esphome {
 namespace dashboard_import {
 
-const std::string &get_package_import_url();
-void set_package_import_url(std::string url);
+const char *get_package_import_url();
+void set_package_import_url(const char *url);
 
 }  // namespace dashboard_import
 }  // namespace esphome

esphome/components/mdns/mdns_component.cpp

@@ -135,8 +135,7 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
 
 #ifdef USE_DASHBOARD_IMPORT
     MDNS_STATIC_CONST_CHAR(TXT_PACKAGE_IMPORT_URL, "package_import_url");
-    txt_records.push_back(
-        {MDNS_STR(TXT_PACKAGE_IMPORT_URL), MDNS_STR(dashboard_import::get_package_import_url().c_str())});
+    txt_records.push_back({MDNS_STR(TXT_PACKAGE_IMPORT_URL), MDNS_STR(dashboard_import::get_package_import_url())});
 #endif
   }
 #endif  // USE_API