fix(player): related marks survive, Restart restarts, and refused pages offer nothing to click

- Every state and Watch-later write goes through features/video/videoWrites,
  which marks the never-refetched lists (related lists, live searches) once
  the server has it; a contract test holds it. The Notification Center's
  undo, the feed's reset and the Watch-later toggles skipped it before.
- Confirmed marks are also kept apart (qk.videoMarks) and laid over the
  related rows: a Show more page landing later rebuilt them from the pages
  it read when it started, and dropped a mark made meanwhile.
- Restart on a related video starts at 0 (the session's stored position
  won before), and on the one already playing it seeks.
- The watched toggle remembers each video's mark: Back showed the opened
  video's launch-time state after a related one was marked.
- The help sheet leaves out the player's keys while a layer above it has
  them waiting.
- After a refusal a retry cannot answer, neither Show more (related) nor
  Load more (live search) is offered; a failed live-search page keeps the
  results already read and says why under them.
- The related cap message counts requests, as the cap does.

frontend/src/modules/home/Home.tsx

@@ -14,7 +14,6 @@ import {
   Star,
 } from "lucide-react";
 import { qk } from "../../lib/queryKeys";
-import { patchRelated } from "../../lib/progressCache";
 import { plexLang } from "../../i18n";
 import {
   api,
@@ -54,6 +53,7 @@ import SegmentedToggle from "../../components/ui/SegmentedToggle";
 import { LoadingState, StateMessage } from "../../components/ui/QueryState";
 import VideoCard, { VideoHoverActions } from "../../features/video/VideoCard";
 import { useVideoActions } from "../../features/video/useVideoActions";
+import { writeVideoState, writeWatchLater } from "../../features/video/videoWrites";
 import { usePlexCardActions } from "../../features/plexCards/usePlexCardActions";
 import { PlexHoverBar, PlexPosterCard } from "../../features/plexCards/plexCards";
 import { usePlaylistsActions } from "../playlists";
@@ -837,11 +837,8 @@ export default function Home() {
       // A full refetch, unlike the feed's stale-mark: these rails are two dozen rows, and marking
       // something watched genuinely changes what the page should answer (it can retire the hero).
       // The feed avoids this because it would refetch ten infinite-query pages per click.
-      void api
-        .setState(id, status)
+      void writeVideoState(qc, id, status)
         .then(() => {
-          // The player's related lists are never refetched: the mark goes into them.
-          patchRelated(qc, id, { status });
           return qc.invalidateQueries({ queryKey: qk.discover() });
         })
         // Without this the rejection escapes unhandled and the click just does nothing — the
@@ -858,7 +855,7 @@ export default function Home() {
 
   const onToggleSave = useCallback(
     (id: string, saved: boolean) => {
-      void (saved ? api.watchLaterAdd(id) : api.watchLaterRemove(id))
+      void writeWatchLater(qc, id, saved)
         .then(() => {
           qc.invalidateQueries({ queryKey: qk.playlists() });
           qc.invalidateQueries({ queryKey: qk.playlist() });