Centre the parts kiosk on the screen instead of hugging the top

plugins/printedparts/frontend/views/PartsKiosk.vue

@@ -222,14 +222,30 @@ function reset() {
   display: flex;
   flex-direction: column;
   align-items: center;
+  /* Centered as one block on the wall-mounted display, not hugging the top.
+     `safe` so a short screen (or a tall error + item card) scrolls from the
+     top instead of clipping the header off the edge, which plain `center`
+     does with no way to scroll back up. */
+  justify-content: center;
+  justify-content: safe center;
   gap: 1.5rem;
 }
 .kiosk-header {
   width: 100%;
   max-width: 40rem;
   display: flex;
-  justify-content: space-between;
+  justify-content: center;
   align-items: center;
+  /* Title sits centered over the panel; Start over is pulled out of the flow
+     so it keeps its top-right corner instead of pushing the title off-center
+     on the steps that show it. */
+  position: relative;
+}
+.kiosk-header .btn {
+  position: absolute;
+  right: 0;
+  top: 50%;
+  transform: translateY(-50%);
 }
 .kiosk-step {
   display: flex;