feat(branding): rebrand footer vendor to MesaStack, trim footer/topbar

- Footer vendor label unified to "MesaStack" across all locales.
- Remove footer Help button; keep version as plain text (no click).
- Remove top-right GitHub star widget (delete unused github-star.tsx);
  keep version as plain text (no click), retain upgrade "New" badge.

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

src/components/footer/index.tsx

@@ -1,8 +1,6 @@
 import { GPUStackVersionAtom } from '@/atoms/user';
-import VersionInfo, { modalConfig } from '@/components/version-info';
-import externalLinks from '@/constants/external-links';
 import { useIntl } from '@umijs/max';
-import { Button, Divider, Modal, Typography } from 'antd';
+import { Divider, Typography } from 'antd';
 import { createStyles } from 'antd-style';
 import { useAtomValue } from 'jotai';
 import styled from 'styled-components';
@@ -33,21 +31,11 @@ const useStyles = createStyles(({ token, css }) => ({
 
 const Footer: React.FC = () => {
   const intl = useIntl();
-  const [modal, contextHolder] = Modal.useModal();
   const { styles } = useStyles();
   const version = useAtomValue(GPUStackVersionAtom);
 
-  const showVersion = () => {
-    modal.info({
-      ...modalConfig,
-      width: 460,
-      content: <VersionInfo intl={intl} />
-    });
-  };
-
   return (
     <>
-      {contextHolder}
       <div className={styles.footer}>
         <div className="footer-content">
           <div className="footer-content-left">
@@ -64,18 +52,7 @@ const Footer: React.FC = () => {
                 </Typography.Link>
               </CompanyWrapper>
               <Divider orientation="vertical" />
-              <Button
-                type="link"
-                size="small"
-                href={externalLinks.documentation}
-                target="_blank"
-              >
-                {intl.formatMessage({ id: 'common.button.help' })}
-              </Button>
-              <Divider orientation="vertical" />
-              <Button type="link" size="small" onClick={showVersion}>
-                {version?.version}
-              </Button>
+              <span>{version?.version}</span>
             </div>
           </div>
         </div>