feat(project-editor): footer validation rules (contact email, social link URLs, payment icons)

Real gaps, not fabricated: isValidEmail existed in primitives.ts but was
never called anywhere; social-link URL check only lived as a per-row
template hint (never blocked publish or set the nav badge); payment icons
with only src or only alt set were silently accepted.

- invalid-contact-email: company.contacts.email must be a valid email (error)
- invalid-social-link-url: footer.socialLinks entries need a valid http(s) URL (warning)
- incomplete-payment-icon: a payment icon needs both src and alt, or neither (warning)

Wired into footer-section via the existing fieldError() pattern. Header has
no equivalent gap today (every header field is a bool/enum, always valid by
construction) so nothing was added there.

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

src/app/features/project-editor/services/project-validator.service.ts

@@ -3,6 +3,7 @@ import { BootstrapConfig } from '../../../shared/models/config';
 import { ProjectEditorSectionId } from '../models/project-editor.model';
 import {
   extractStyleBlocks,
+  isValidEmail,
   isValidHexColor,
   isValidHttpUrl,
   normalizeRoute,
@@ -56,6 +57,9 @@ export class ProjectValidator {
       ...this.cssIssues(bootstrap),
       ...this.translationIssues(bootstrap),
       ...this.layoutIssues(bootstrap),
+      ...this.footerContactIssues(bootstrap),
+      ...this.footerSocialLinkIssues(bootstrap),
+      ...this.footerPaymentIconIssues(bootstrap),
     ];
   }
 
@@ -222,4 +226,26 @@ export class ProjectValidator {
       ? [error('invalid-layouts', 'builder.validationInvalidLayouts', 'theme', 'layout.type')]
       : [];
   }
+
+  private footerContactIssues(bootstrap: BootstrapConfig): ProjectValidationIssue[] {
+    const email = bootstrap.company?.contacts?.email;
+    return !email || isValidEmail(email)
+      ? []
+      : [error('invalid-contact-email', 'builder.validationInvalidContactEmail', 'footer', 'company.contacts.email')];
+  }
+
+  private footerSocialLinkIssues(bootstrap: BootstrapConfig): ProjectValidationIssue[] {
+    const hasInvalidUrl = (bootstrap.footer?.socialLinks ?? []).some(link => !!link.url && !isValidHttpUrl(link.url));
+    return hasInvalidUrl
+      ? [warning('invalid-social-link-url', 'builder.validationInvalidSocialLinkUrl', 'footer', 'footer.socialLinks')]
+      : [];
+  }
+
+  /** A payment icon row with only one of src/alt set is a broken image reference or missing accessibility text. */
+  private footerPaymentIconIssues(bootstrap: BootstrapConfig): ProjectValidationIssue[] {
+    const hasIncompleteRow = (bootstrap.footer?.paymentIcons ?? []).some(icon => !!icon.src !== !!icon.alt);
+    return hasIncompleteRow
+      ? [warning('incomplete-payment-icon', 'builder.validationIncompletePaymentIcon', 'footer', 'footer.paymentIcons')]
+      : [];
+  }
 }