Add admin-editable QR code image to homepage share section

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/AdminPage.tsx

@@ -870,6 +870,7 @@ const FIELDS: Array<{ key: StringField; label: string; multiline?: boolean; sect
   { key: 'studyGuideUrl', label: 'Study Guide URL (Amazon link)', section: 'series' },
   { key: 'shareHeading', label: 'Share Section — Heading', section: 'share' },
   { key: 'shareP', label: 'Share Section — Paragraph', multiline: true, section: 'share' },
+  { key: 'shareQrImageUrl', label: 'Share Section — QR Code Image', section: 'share' },
   { key: 'prismVideoUrl', label: 'PRISM — Video URL', section: 'prism' },
   { key: 'prismEyebrow', label: 'PRISM — Eyebrow', section: 'prism' },
   { key: 'prismHeading', label: 'PRISM — Heading', section: 'prism' },
@@ -3577,6 +3578,8 @@ export default function AdminPage({ content, onSave, onLogout }: Props) {
                   {multiline
                     ? <textarea id={`field-${key}`} value={form[key] as string} onChange={e => handleChange(key, e.target.value)} rows={4} />
                     : <input id={`field-${key}`} type="text" value={form[key] as string} onChange={e => handleChange(key, e.target.value)} />}
+                  {key.includes('ImageUrl') && renderImageAssetSelector(form[key] as string, value => handleChange(key, value), `field-${key}-asset`)}
+                  {key.includes('ImageUrl') && renderImagePreview(form[key] as string, `${label} preview`)}
                 </div>
               ))}