fix(workbench): drop the not-yet-live openkb.ai website link from About

The About tab linked a "Website openkb.ai" that does not exist yet; remove the
link entry and its i18n key (both locales). The Globe icon stays (still used by
the Vectify AI company link).

Claude-Session: https://claude.ai/code/session_01XMxbhmAkxxVV8CFWCZDBaG

Author: KylinMountain

frontend/src/components/AboutTab.tsx

@@ -5,7 +5,6 @@ import { getMeta } from '@/api/meta'
 
 // Labels resolve at render time via `t(\`about.links.${id}\`)`; href/icon are code.
 const LINKS: { id: string; href: string; icon: typeof Globe }[] = [
-  { id: 'site', href: 'https://openkb.ai', icon: Globe },
   { id: 'repo', href: 'https://github.com/VectifyAI/OpenKB', icon: Github },
   { id: 'pageindex', href: 'https://github.com/VectifyAI/PageIndex', icon: Github },
   { id: 'docs', href: 'https://docs.pageindex.ai', icon: BookOpen },

frontend/src/locales/en/settings.json

@@ -26,7 +26,6 @@
   },
   "about": {
     "links": {
-      "site": "Website openkb.ai",
       "repo": "GitHub repo",
       "pageindex": "PageIndex (retrieval engine)",
       "docs": "Docs docs.pageindex.ai",

frontend/src/locales/zh/settings.json

@@ -26,7 +26,6 @@
   },
   "about": {
     "links": {
-      "site": "官网 openkb.ai",
       "repo": "GitHub 仓库",
       "pageindex": "PageIndex（底层检索引擎）",
       "docs": "文档 docs.pageindex.ai",