Kiosk: System Name storage, validation, sync, and sent on license validation

Adds local System Name persistence (trimmed, 1-40) in system_kv, an
injectable sync module with conflict/invalid revert and a pending-sync
flag, a background SystemNameSync worker (retries on boot and on a timer),
and api_client support for PUT /licenses/{key}/system-name plus the
additive systemName field/systemNameStatus on license validation. The
license service sends the stored name and applies the status. Covers
validation, pending retry, and conflict revert with a faked HTTP layer.

src/network/license_service.h

@@ -1,6 +1,8 @@
 #pragma once
 
 #include "db/database_manager.h"
+#include "network/api_client.h"
+#include <functional>
 #include <string>
 
 namespace radiantwave::license {
@@ -28,6 +30,16 @@ constexpr long long GRACE_PERIOD_SECONDS = 7LL * 24 * 60 * 60;
 Result validateStoredLicense(radiantwave::db::DatabaseManager& db,
                              std::string* outErrorMessage = nullptr);
 
+// Injectable core of validateStoredLicense: performs the given validation call
+// instead of the live portal. On success it stamps "last verified" and applies
+// any advisory `systemNameStatus` to the local System Name state.
+using ValidateFn = std::function<api::LicenseResult(
+    const std::string& key, const std::string& email, const std::string& systemName)>;
+
+Result validateStoredLicenseWith(radiantwave::db::DatabaseManager& db,
+                                 const ValidateFn& validate,
+                                 std::string* outErrorMessage = nullptr);
+
 // Records the current time as the "last verified" stamp of the license. Called
 // after every successful server validation so the offline grace window starts
 // (or is extended) from the most recent confirmation.