CSS:
- #seek-row and #controls-row: flexbox base (flex: 1 on children,
  margin-left gaps) + CSS Grid enhancement via @supports (display: grid)
- #playlist-overlay: replaced inset: 0 with explicit top/right/bottom/left
  (inset shorthand not available before iOS 14.5)
- All flex-gap usages: adjacent-sibling margin fallbacks as the base;
  gap values restored via a single @supports (gap: 1px) block at the end
  (flex gap not available before iOS 14.5 / Safari 14.1)
- Added -webkit- prefixes for user-select, flex, transition, transform
  throughout to be safe on older WebKit

JS:
- Added apiFetch() wrapper: uses native fetch() when available (iOS 10.3+),
  falls back to a minimal XMLHttpRequest shim for iOS 9 and older.
  Matches the exact subset of the fetch API the app uses: .json(),
  method, headers, body.
- Replaced all four fetch() call sites with apiFetch()

Result: layout and all API calls (rating, killist, playlist) work on
iOS 9 / iPad 2. Modern browsers get the exact same behaviour as before
via the @supports enhancements.

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