refactor: hook dependencies name everything the hooks read

The 12 react-hooks/exhaustive-deps warnings the gate let through:
- ShareDialog and YearFilter built a fresh [] per render while their query loaded, so their
  memos recomputed on every render; they share one empty list now.
- VideoEditor's drag effect called a seek/moveBoundary recreated each render; both are stable
  callbacks in its deps.
- WizardProvider re-checks onboarding on exactly the fields it reads (not the me object, whose
  60 s refetch would reopen a closed wizard).
- Channels, Feed and PlexPlayer list the stable values they already used.
- The player's keydown effect is bound once on purpose (its helpers read refs): said so, with a
  disable, as the codebase's other deliberate sites do.
- dialogFocus and the YouTube player's cleanup read refs React may already have let go of; they
  use what they captured when the effect ran.

frontend/src/components/PlexPlayer.tsx

@@ -227,12 +227,13 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
   // Must be stable: an inline arrow would detach (null) and re-attach the node on every render,
   // and the fade's node-state ref would re-render in response — a loop. `fade.ref` is a setState.
   const tracksFade = useScrollFade();
+  const tracksFadeRef = tracksFade.ref;
   const setTracksNode = useCallback(
     (node: HTMLElement | null) => {
       tracksRef.current = node as HTMLDivElement | null;
-      tracksFade.ref(node);
+      tracksFadeRef(node);
     },
-    [tracksFade.ref],
+    [tracksFadeRef],
   );
   // The keyboard cheat sheet is app-wide now (ui/KeyboardHelp, opened by the global "h"), not this
   // player's own overlay. Mirror its open state into a ref because usePlayerVolume still needs to