Add admin-editable QR code image to homepage share section

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

src/content.ts

@@ -174,6 +174,7 @@ export interface SiteContent {
   // ── Share ──
   shareHeading: string
   shareP: string
+  shareQrImageUrl: string
   // ── PRISM Video ──
   prismVideoUrl: string
   prismEyebrow: string
@@ -363,6 +364,7 @@ export const DEFAULTS: SiteContent = {
   colossiansStudySections: DEFAULT_COLOSSIANS_STUDY_SECTIONS,
   shareHeading: 'Help one more person hear the Word this week.',
   shareP: 'Scan the QR code or text the show link to a friend who needs encouragement today.',
+  shareQrImageUrl: '/images/qr-code.jpg',
   prismVideoUrl: '/images/PRISM.mp4',
   prismEyebrow: 'Featured Video',
   prismHeading: 'PRISM',