refactor(nav): read navigation from context, drop the prop-drilling

VideoCard/PlayerModal read openChannel from useNavigationActions (the memo'd
VideoCard subscribes to the STABLE actions context, so a page/channel change
no longer re-renders it); NavSidebar/Header read page/setPage; ChannelPage
reads closeChannel; NotificationsPanel reads setPage. App sheds the matching
props, and Feed/VirtualFeed no longer thread onOpenChannel at all.

frontend/src/components/PlayerModal.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useMemo, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { createPortal } from "react-dom";
+import { useNavigationActions } from "./NavigationProvider";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import { AlertTriangle, ArrowLeft, Check, CheckCheck, ChevronLeft, ChevronRight, ExternalLink, Repeat, Repeat1, Settings, Shuffle, SkipBack, SkipForward, Volume2, VolumeX, X } from "lucide-react";
 import Avatar from "./Avatar";
@@ -55,7 +56,6 @@ export default function PlayerModal({
   startIndex,
   onClose,
   onState,
-  onOpenChannel,
 }: {
   video: Video;
   // Where to start the opened video: a number of seconds (0 = Restart), or null/undefined
@@ -70,9 +70,9 @@ export default function PlayerModal({
   onState: (id: string, status: string) => void;
   // Open the active video's channel page in-app (closes the player first). The small external
   // icon next to the name keeps the open-on-YouTube behaviour.
-  onOpenChannel?: (channelId: string, channelName?: string) => void;
 }) {
   const { t, i18n } = useTranslation();
+  const { openChannel } = useNavigationActions();
   const qc = useQueryClient();
   const descFade = useScrollFade();
   // Browser/mouse Back closes the player instead of leaving the page.
@@ -840,16 +840,15 @@ export default function PlayerModal({
               <div className="flex items-center gap-1.5 shrink-0 min-w-0">
                 <button
                   onClick={() => {
-                    if (!onOpenChannel) return onClose();
                     const cid = active.channel_id;
                     const cname = active.channel_title ?? undefined;
                     // Closing the player pops its own history entry (useBackToClose → history.back()).
                     // Open the channel only AFTER that pop's popstate — pushing the channel entry
                     // before it would let the back remove it again (the bug: clicking the name only
-                    // closed the player). One-shot listener fires after App's popstate handler.
+                    // closed the player). One-shot listener fires after the popstate handler.
                     const open = () => {
                       window.removeEventListener("popstate", open);
-                      onOpenChannel(cid, cname);
+                      openChannel(cid, cname);
                     };
                     window.addEventListener("popstate", open);
                     onClose();