feat(downloads): editable details with clickable channel and extra links

The edit (pencil) action now edits a download's full display metadata — title,
channel name, channel link and any number of extra reference URLs — instead of
just the name. The channel and links render as clickable links on the library
card, and the channel link is auto-filled from the source (yt-dlp channel_url)
when available. Shared watch pages resolve the same per-download overrides, so a
rename/channel/link edit is reflected on the public /watch page too, with every
link clickable.

Adds migration 0049 (media_assets.uploader_url; download_jobs.display_uploader,
display_uploader_url, extra_links) and generalizes the rename endpoint into a
metadata update with URL validation. EN/HU/DE strings included.

frontend/src/components/WatchPage.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useState } from "react";
-import { Download, Lock, PlayCircle } from "lucide-react";
+import { Download, Link2, Lock, PlayCircle } from "lucide-react";
 
 // Standalone, login-free video page for a shared /watch/<token> link. Rendered OUTSIDE the app
 // tree (no auth, no providers) — like the /privacy and /terms pages. Uses plain fetch and a tiny
@@ -9,11 +9,24 @@ type Meta = {
   needs_password: boolean;
   title?: string | null;
   uploader?: string | null;
+  uploader_url?: string | null;
+  source_url?: string | null;
+  extra_links?: string[];
   duration_s?: number | null;
   allow_download?: boolean;
   file_url?: string;
 };
 
+// Compact display of a URL: drop the protocol + trailing slash so it fits on one line.
+function displayUrl(url: string): string {
+  try {
+    const u = new URL(url);
+    return (u.host + u.pathname + u.search).replace(/\/$/, "");
+  } catch {
+    return url;
+  }
+}
+
 const STR = {
   en: {
     loading: "Loading…",
@@ -24,6 +37,7 @@ const STR = {
     watch: "Watch",
     wrong: "Wrong password.",
     download: "Download",
+    links: "Links",
     brand: "Shared via Siftlode",
   },
   hu: {
@@ -35,6 +49,7 @@ const STR = {
     watch: "Megnézem",
     wrong: "Hibás jelszó.",
     download: "Letöltés",
+    links: "Linkek",
     brand: "Megosztva a Siftlode-dal",
   },
   de: {
@@ -46,6 +61,7 @@ const STR = {
     watch: "Ansehen",
     wrong: "Falsches Passwort.",
     download: "Herunterladen",
+    links: "Links",
     brand: "Geteilt über Siftlode",
   },
 } as const;
@@ -165,7 +181,19 @@ export default function WatchPage() {
             <div className="mt-3 flex items-start gap-3">
               <div className="min-w-0 flex-1">
                 <h1 className="text-lg font-semibold leading-snug">{meta.title || "Video"}</h1>
-                {meta.uploader && <div className="text-sm text-slate-400">{meta.uploader}</div>}
+                {meta.uploader &&
+                  (meta.uploader_url ? (
+                    <a
+                      href={meta.uploader_url}
+                      target="_blank"
+                      rel="noopener noreferrer"
+                      className="text-sm text-slate-400 hover:text-teal-400 hover:underline"
+                    >
+                      {meta.uploader}
+                    </a>
+                  ) : (
+                    <div className="text-sm text-slate-400">{meta.uploader}</div>
+                  ))}
               </div>
               {meta.allow_download && (
                 <a
@@ -176,6 +204,25 @@ export default function WatchPage() {
                 </a>
               )}
             </div>
+            {(meta.source_url || (meta.extra_links && meta.extra_links.length > 0)) && (
+              <div className="mt-3 flex flex-col gap-1.5">
+                {[meta.source_url, ...(meta.extra_links ?? [])]
+                  .filter((u): u is string => !!u)
+                  .map((url) => (
+                    <a
+                      key={url}
+                      href={url}
+                      target="_blank"
+                      rel="noopener noreferrer"
+                      title={url}
+                      className="inline-flex items-center gap-1.5 text-sm text-slate-400 hover:text-teal-400 hover:underline min-w-0"
+                    >
+                      <Link2 className="w-3.5 h-3.5 shrink-0" />
+                      <span className="truncate">{displayUrl(url)}</span>
+                    </a>
+                  ))}
+              </div>
+            )}
           </div>
         )}
       </div>