improvement(welcome): gallery landing, refreshed copy, name-free screenshots

Rebuild the landing preview into a per-module screenshot gallery (feed hero + channels, playlists, search, player, downloads, Plex), reusing the existing Preview/Lightbox. Rewrite the hero + feature copy in a plainer, concise tone that reflects the current modules (Download Center, Plex, two-way playlists), in EN and HU. Regenerate all screenshots name-free. Bring the README up to date: fix the broken landing image, add the Plex feature, and correct the now-temporary YouTube-search behaviour.

frontend/src/components/Welcome.tsx

@@ -2,7 +2,9 @@ import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import {
   ArrowRight,
+  Clapperboard,
   Code2,
+  Download,
   Expand,
   Filter,
   Inbox,
@@ -115,20 +117,19 @@ export default function Welcome() {
           </div>
         </section>
 
-        {/* Secondary showcase — smaller thumbnails; click to view full size. */}
-        <section className="mt-12 flex flex-wrap justify-center gap-4">
-          <Preview
-            src="/welcome/channels.webp"
-            label={t("welcome.preview.channels")}
-            className="w-full sm:w-72 aspect-[4/3]"
-            onOpen={open}
-          />
-          <Preview
-            src="/welcome/playlists.webp"
-            label={t("welcome.preview.playlists")}
-            className="w-full sm:w-72 aspect-[4/3]"
-            onOpen={open}
-          />
+        {/* Gallery — one shot per module; click any to view it full size. */}
+        <section className="mt-12">
+          <div className="grid sm:grid-cols-2 lg:grid-cols-3 gap-4">
+            {GALLERY.map((g) => (
+              <Preview
+                key={g.key}
+                src={g.src}
+                label={t(`welcome.preview.${g.key}`)}
+                className="aspect-video"
+                onOpen={open}
+              />
+            ))}
+          </div>
         </section>
       </main>
 
@@ -159,12 +160,25 @@ export default function Welcome() {
   );
 }
 
+// The screenshot gallery below the hero — one shot per module, each opening full-size in the
+// lightbox. Order roughly follows the nav rail; the feed leads as the hero above the fold.
+const GALLERY: { key: string; src: string }[] = [
+  { key: "channels", src: "/welcome/channels.webp" },
+  { key: "playlists", src: "/welcome/playlists.webp" },
+  { key: "search", src: "/welcome/search.webp" },
+  { key: "player", src: "/welcome/player.webp" },
+  { key: "downloads", src: "/welcome/downloads.webp" },
+  { key: "plex", src: "/welcome/plex.webp" },
+];
+
 const FEATURES: { key: string; icon: LucideIcon }[] = [
   { key: "readable", icon: Filter },
   { key: "neverMiss", icon: Inbox },
   { key: "search", icon: Search },
   { key: "playlists", icon: ListVideo },
   { key: "player", icon: PlayCircle },
+  { key: "downloads", icon: Download },
+  { key: "plex", icon: Clapperboard },
   { key: "private", icon: Lock },
 ];