fix(mobile): address iPhone layout issues across rankings, detail, compare

- rankings: hide Type/Action columns on mobile so metric value stays visible;
  ensure filter selects and table wrapper stay within viewport
- school detail: add min-width:0 / max-width:100% containment so internal
  overflow-x wrappers actually clip rather than pushing the page wider;
  explicit line-height on Ofsted grade badges to fix glyph clipping
- compare: sticky first column on the Detailed Comparison table so the Year
  labels remain visible while horizontally scrolling school columns
- search: shorten placeholder to "School name or postcode" so it fits mobile
  input width
- globals: overflow-x:clip safety net on .main wrapper

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextjs-app/components/SchoolSearchModal.tsx

@@ -91,7 +91,7 @@ export function SchoolSearchModal({ isOpen, onClose }: SchoolSearchModalProps) {
             type="text"
             value={searchTerm}
             onChange={(e) => handleSearchChange(e.target.value)}
-            placeholder="Search by school or postcode ..."
+            placeholder="School name or postcode"
             className={styles.searchInput}
             autoFocus
           />