feat: add clear HMS errors button to dismiss stale print errors

Add a "Clear Errors" button to the HMS error modal that sends
clean_print_error via MQTT and locally clears hms_errors for
immediate UI feedback. Useful for dismissing stale print_error
values that persist after print cancellation or transient events.

frontend/src/api/client.ts

@@ -2344,6 +2344,10 @@ export const api = {
       }
     ),
 
+  // HMS Errors
+  clearHMSErrors: (printerId: number) =>
+    request<{ success: boolean; message: string }>(`/printers/${printerId}/hms/clear`, { method: 'POST' }),
+
   // AMS Control
   refreshAmsSlot: (printerId: number, amsId: number, slotId: number) =>
     request<{ success: boolean; message: string }>(