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

scripts/docker-prod-common.sh

@@ -137,7 +137,7 @@ start_prod_services() {
 
   for service in "${services[@]}"; do
     case "${service}" in
-      api|marketplace|dashboard|admin)
+      api|storefront|dashboard|admin)
         needs_migrations=1
         break
         ;;
@@ -181,7 +181,7 @@ login_registry_if_configured() {
 
 pull_prod_release_images() {
   require_release_image
-  prod_compose pull migrate api marketplace dashboard admin
+  prod_compose pull migrate api storefront dashboard admin
 }
 
 run_prod_migrations() {