refactor: rename marketplace to storefront across the entire monorepo

Comprehensive rename of all marketplace references to storefront:
- API module: apps/api/src/modules/marketplace/ → storefront/
- Components: MarketplaceHeader → StorefrontHeader, MarketplaceShell →
  StorefrontShell, MarketplaceFooter → StorefrontFooter
- Types: marketplace-homepage.ts → storefront-homepage.ts
- Test files: employee-marketplace-* → employee-storefront-*
- All source code identifiers, imports, route paths, and strings
- Documentation (docs/), CI config (.gitlab-ci.yml), scripts
- Dashboard, admin, storefront workspace references
- Prisma field names preserved (isListedOnMarketplace, marketplaceRating,
  marketplaceFunnelEvent) as they map to database schema

Validation:
- API type-check: 0 errors
- Storefront type-check: 0 errors
- Dashboard type-check: 0 errors
- Full monorepo type-check: only pre-existing admin TS18046

apps/api/src/modules/admin/admin.service.ts

@@ -3,7 +3,7 @@ import crypto from 'crypto'
 import { authenticator } from 'otplib'
 import { signActorToken } from '../../security/tokens'
 import qrcode from 'qrcode'
-import { getMarketplaceHomepageContent, saveMarketplaceHomepageContent } from '../../services/platformContentService'
+import { getStorefrontHomepageContent, saveStorefrontHomepageContent } from '../../services/platformContentService'
 import { sendTransactionalEmail } from '../../services/notificationService'
 import * as presenter from './admin.presenter'
 import * as repo from './admin.repo'
@@ -402,16 +402,16 @@ export function issueBillingRefund(
   return billingService.issueRefund(invoiceId, data, adminId, ip)
 }
 
-export function getMarketplaceHomepage() {
-  return getMarketplaceHomepageContent()
+export function getStorefrontHomepage() {
+  return getStorefrontHomepageContent()
 }
 
-export async function updateMarketplaceHomepage(homepage: any, adminId: string, ip?: string) {
-  const saved = await saveMarketplaceHomepageContent(homepage)
+export async function updateStorefrontHomepage(homepage: any, adminId: string, ip?: string) {
+  const saved = await saveStorefrontHomepageContent(homepage)
   await repo.createAuditLog({
     adminUserId: adminId,
     action: 'UPDATE',
-    resource: 'MarketplaceHomepage',
+    resource: 'StorefrontHomepage',
     after: toAuditJson(saved),
     ipAddress: ip,
     userAgent: undefined,