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/PlayerModal.tsx

@@ -489,6 +489,10 @@ export default function PlayerModal({
       window.removeEventListener("keydown", onKey);
       // (The debounced volume write is flushed by useYtVolume's own unmount cleanup.)
     };
+    // Bound once per player on purpose: every helper the handler calls reads its live state through
+    // a ref (playerRef, navRef, maximizedRef, isFullscreenRef, the volume hook's own ref), so
+    // re-binding on each render would only churn the listener, never change what a key does.
+    // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [onClose]);
 
   // Create the player, resume from the saved position, checkpoint progress, and auto-mark watched at