fix: address reader-UI feedback (shorts, search, tags, login, UX)

- Shorts: confirm via youtube.com/shorts/<id> probe (SOCS cookie bypasses the
  consent redirect) instead of a 60s heuristic; concurrent probing, shorts_probed
  flag, scheduled refinement (migration 0005)
- Search: match title + channel name only (descriptions caused noisy results)
- Faceted tag filtering: AND across categories (language AND topic narrows),
  OR within a category; any/all toggle applies to topics
- Language detection: majority vote over individual titles (fixes misdetections
  like multipoleguy -> English; drops bogus Polish/Romanian)
- Login: drop forced consent so returning sign-in is quick (select_account)
- Feed cards: clickable channel name (opens channel), persistent saved badge,
  undo toast on hide, Hidden view to restore; tag chips show counts in tooltip

frontend/src/components/Feed.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState } from "react";
 import { useInfiniteQuery } from "@tanstack/react-query";
 import { api, type FeedFilters, type Video } from "../lib/api";
+import { toast } from "../lib/toast";
 import VideoCard from "./VideoCard";
 
 const PAGE = 60;
@@ -43,12 +44,19 @@ export default function Feed({
   function onState(id: string, status: string) {
     setOverrides((o) => ({ ...o, [id]: status }));
     api.setState(id, status).catch(() => {});
+    if (status === "hidden") {
+      toast("Video hidden", { label: "Undo", onClick: () => onState(id, "new") });
+    }
   }
 
   const items: Video[] = (query.data?.pages ?? [])
     .flatMap((p) => p.items)
     .map((v) => (overrides[v.id] ? { ...v, status: overrides[v.id] } : v))
-    .filter((v) => overrides[v.id] !== "hidden");
+    .filter((v) => {
+      const ov = overrides[v.id];
+      // In the Hidden view, drop just-unhidden items; elsewhere drop just-hidden ones.
+      return filters.show === "hidden" ? ov !== "new" : ov !== "hidden";
+    });
 
   if (query.isLoading) return <div className="p-8 text-muted">Loading feed…</div>;
   if (query.isError) return <div className="p-8 text-muted">Couldn't load the feed.</div>;