feat(search): ephemeral results UX, count selector, channel blocklist (frontend)

- Live-search view: a results-count selector (20/40/60/100) replaces manual load-more (the free
  scrape source pages until that many are gathered); an 'these results are temporary' banner with
  a 'Clear now' button that discards them 'as if never added' (api.clearSearch) and returns to
  the feed.
- Channel blocklist: a Block/Unblock toggle + 'Blocked' badge on the channel page (blocked
  channels don't auto-explore and their videos are hidden), and a 'Blocked channels' section in
  the Channel manager with one-click unblock. ChannelDetail.blocked from the backend.
- Admin: a 'Purge discovery' button on the Scheduler page (immediate un-kept search/explore
  cleanup). EN/HU/DE throughout.

frontend/src/components/Channels.tsx

@@ -4,6 +4,7 @@ import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import {
   ArrowDown,
   ArrowUp,
+  Ban,
   Check,
   Eye,
   EyeOff,
@@ -87,7 +88,15 @@ export default function Channels({
   const channelsQuery = useQuery({ queryKey: ["channels"], queryFn: api.channels });
   const tagsQuery = useQuery({ queryKey: ["tags"], queryFn: api.tags });
   const statusQuery = useQuery({ queryKey: ["my-status"], queryFn: api.myStatus });
+  const blockedQuery = useQuery({ queryKey: ["blocked-channels"], queryFn: api.blockedChannels });
   const [tagManagerOpen, setTagManagerOpen] = useState(false);
+  const unblock = useMutation({
+    mutationFn: (id: string) => api.unblockChannel(id),
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: ["blocked-channels"] });
+      qc.invalidateQueries({ queryKey: ["feed"] });
+    },
+  });
 
   const invalidate = () => {
     qc.invalidateQueries({ queryKey: ["channels"] });
@@ -567,6 +576,37 @@ export default function Channels({
           emptyText={t("channels.empty")}
         />
       )}
+
+      {/* Blocked channels — videos from these are hidden everywhere and dropped from live search. */}
+      {(blockedQuery.data?.length ?? 0) > 0 && (
+        <div className="mt-6 border-t border-border pt-4">
+          <div className="flex items-center gap-2 mb-2">
+            <Ban className="w-4 h-4 text-muted" />
+            <span className="text-xs uppercase tracking-wide text-muted">
+              {t("channels.blocked.title")}
+            </span>
+          </div>
+          <div className="flex flex-wrap gap-1.5">
+            {blockedQuery.data!.map((c) => (
+              <span
+                key={c.id}
+                className="inline-flex items-center gap-1.5 text-xs pl-2.5 pr-1 py-1 rounded-full bg-card border border-border"
+              >
+                {c.title ?? c.id}
+                <button
+                  onClick={() => unblock.mutate(c.id)}
+                  title={t("channel.unblock")}
+                  aria-label={t("channel.unblock")}
+                  className="rounded-full p-0.5 text-muted hover:text-danger transition"
+                >
+                  <X className="w-3 h-3" />
+                </button>
+              </span>
+            ))}
+          </div>
+          <p className="text-[11px] text-muted mt-2">{t("channels.blocked.hint")}</p>
+        </div>
+      )}
     </div>
     </>
   );