refactor(ui): update pokemon detail grid layout and section title

Apply single-column stack layout to detail grids
Shorten the related items section title for conciseness

frontend/src/styles/main.css

@@ -913,6 +913,10 @@ button:disabled,
   gap: 16px;
 }
 
+.detail-grid--stack {
+  grid-template-columns: 1fr;
+}
+
 .habitat-detail-stack {
   display: grid;
   gap: 16px;