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/ShareDialog.tsx

@@ -10,19 +10,23 @@ import { notify } from "../lib/notifications";
 import { notifyActionError } from "../lib/actionErrors";
 import { copyText } from "../lib/clipboard";
 import { formatDate } from "../lib/format";
-import { api, type DownloadJob, type ShareLink } from "../lib/api";
+import { api, type DownloadJob, type ShareLink, type ShareRecipient } from "../lib/api";
 import { inputCls } from "./ui/form";
 import { Button } from "./ui/Button";
 const EXPIRY_DAYS = [null, 1, 7, 30] as const;
 
 // --- share with a registered user (ACL) -----------------------------------------------------
 
+// One shared empty list while the recipients load: a fresh `[]` per render made `filtered` below
+// recompute on every render.
+const NO_RECIPIENTS: ShareRecipient[] = [];
+
 function UserShare({ job }: { job: DownloadJob }) {
   const { t } = useTranslation();
   const [q, setQ] = useState("");
   const [open, setOpen] = useState(false);
   const recipients = useQuery({ queryKey: qk.shareRecipients(), queryFn: api.shareRecipients });
-  const list = recipients.data ?? [];
+  const list = recipients.data ?? NO_RECIPIENTS;
   const filtered = useMemo(() => {
     const s = q.trim().toLowerCase();
     if (!s) return list.slice(0, 8);