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-deploy.sh

@@ -25,9 +25,9 @@ echo "Running database migrations"
 run_prod_migrations
 
 echo "Starting application services"
-prod_compose up -d api marketplace dashboard admin
+prod_compose up -d api storefront dashboard admin
 wait_for_healthy api 180
-wait_for_healthy marketplace 180
+wait_for_healthy storefront 180
 wait_for_healthy dashboard 180
 wait_for_healthy admin 180