fix(chapters): address review findings + trickplay polish

Copilot + CodeRabbit review findings:
- React.memo ChapterTicks and ChapterList (project guideline: hot-path
  components must use React.memo to cut redraw work during control
  updates).
- chapterNameAt now sorts the chapter array once instead of twice per
  call. The previous version went through currentChapterIndex
  (chapterStartsMs + sort) then sortedChapters (sort again). Runs on
  every playback tick, so the duplicate work added up.
- Import getUserLibraryApi from the public barrel
  (@jellyfin/sdk/lib/utils/api) instead of the deep internal path
  (@jellyfin/sdk/lib/utils/api/user-library-api) to match the rest of
  the codebase and avoid coupling to SDK file layout.

TrickplayBubble polish:
- Sit just above the slider (bottom: 0) so the bubble no longer overlaps
  the progress bar.
- Move the chapter-name + timestamp overlay to the bottom-left of the
  preview frame, smaller font, in front of the surrounding overlays
  (zIndex + elevation).

BottomControls cleanup:
- Drop dev-only "pick one to test" comment in favour of a one-line note
  on TICK_HEIGHT.
- Inline scrubMs into its useMemo callback so the scrub-chapter-name
  lookup only recomputes while a slide is active.

components/video-player/controls/BottomControls.tsx

@@ -189,7 +189,6 @@ export const BottomControls: FC<BottomControlsProps> = ({
               onPress={() => setChapterListVisible(true)}
               hitSlop={10}
               className='justify-center mr-4'
-              style={{ marginTop: 10 }}
               accessibilityRole='button'
               accessibilityLabel={t("chapters.open")}
             >

components/video-player/controls/TrickplayBubble.tsx

@@ -52,8 +52,9 @@ export const TrickplayBubble: FC<TrickplayBubbleProps> = ({
       style={{
         position: "absolute",
         left: -62,
-        // Drop the bubble closer to the slider — less floating-high feel.
-        bottom: -20,
+        // Sit just above the slider — high enough not to overlap the
+        // progress bar, low enough to feel anchored to the thumb.
+        bottom: 0,
         paddingTop: 12,
         paddingBottom: 5,
         width: tileWidth * 1.5,