fix(project-editor): validate footer payment/social links, add footer logo picker

- header-section: raw checkboxes -> app-toggle, wrap in SectionCard
- footer-section: replace unvalidated pipe-delimited textareas for payment
  icons/social links with KeyValueEditor + MediaPickerComponent, add missing
  footer logo picker, validate social link URLs (http/https), wrap in SectionCard
- i18n: add footer logo / key-value-editor labels and URL validation message

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/en.ts

@@ -452,6 +452,15 @@ export const en: Translations = {
     copyright: 'Copyright',
     paymentIcons: 'Payment Icons',
     socialLinks: 'Social Links',
+    footerLogo: 'Footer Logo',
+    addPaymentIcon: 'Add Payment Icon',
+    removePaymentIcon: 'Remove',
+    iconAltLabel: 'Icon Label',
+    addSocialLink: 'Add Social Link',
+    removeSocialLink: 'Remove',
+    socialLinkLabel: 'Platform',
+    socialLinkUrl: 'URL',
+    invalidUrl: 'Enter a valid URL starting with http:// or https://.',
     createPage: 'Create Page',
     deletePage: 'Delete Page',
     pageId: 'Page ID',
@@ -590,6 +599,9 @@ export const en: Translations = {
     copyrightDesc: 'Copyright line shown at the bottom of every page.',
     paymentIconsDesc: 'One payment icon entry per line (image URL and label) shown in the footer.',
     socialLinksDesc: 'One social link entry per line (platform and URL) shown in the footer.',
+    footerLogoDesc: 'Logo shown in the footer, if different from the header logo.',
+    iconAltLabelDesc: 'Alt text describing the payment icon for accessibility.',
+    socialLinkUrlDesc: 'Full URL to the social media profile, must start with http:// or https://.',
     staticPagesFieldDesc: 'Static pages (about, terms, privacy, etc.) linked from the footer.',
     sectionVisibleDesc: 'Whether this homepage section is shown to shoppers.',
     layoutStrategyLabel: 'Layout strategy',