fix: 链接预览强调色按域名兜底,腾讯会议不再用黑色

部分站点(如 meeting.tencent.com)返回 themeColor=#000000,在深色气泡上看不见。
按域名覆盖为品牌金色,其余仍优先用 themeColor。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/messageStream/LinkPreviewCard.tsx

@@ -1,5 +1,27 @@
 import type { LinkPreview } from "../../types/post";
 
+const LINK_ACCENT = "#eeb726";
+
+const DOMAIN_ACCENT_OVERRIDES: Array<[string, string]> = [
+  // Tencent Meeting returns themeColor="#000000", which disappears on the
+  // dark bubble surface. Keep it consistent with inline link color instead.
+  ["meeting.tencent.com", LINK_ACCENT],
+];
+
+function linkPreviewAccent(preview: LinkPreview): string {
+  const url = preview.canonicalUrl || preview.url;
+  try {
+    const host = new URL(url).hostname.replace(/^www\./, "");
+    const match = DOMAIN_ACCENT_OVERRIDES.find(
+      ([domain]) => host === domain || host.endsWith(`.${domain}`),
+    );
+    if (match) return match[1];
+  } catch {
+    // Ignore malformed preview URLs and fall back below.
+  }
+  return preview.themeColor || LINK_ACCENT;
+}
+
 /**
  * Telegram-style rich preview card for a single URL embedded in a post.
  *
@@ -8,7 +30,7 @@ import type { LinkPreview } from "../../types/post";
  * that opens `canonicalUrl` in a new tab.
  */
 export function LinkPreviewCard({ preview }: { preview: LinkPreview }) {
-  const accent = preview.themeColor || "#EEB726";
+  const accent = linkPreviewAccent(preview);
   const hasUsefulText =
     preview.title.length > 0 || preview.description.length > 0;
   if (!hasUsefulText && !preview.imageUrl) return null;