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

storefront/src/middleware.test.ts

@@ -63,7 +63,7 @@ beforeEach(() => {
   nextServer.redirect.mockClear()
 })
 
-describe('marketplace proxy language bootstrap', () => {
+describe('storefront proxy language bootstrap', () => {
 
   it('rejects proxy subrequest headers before language handling', async () => {
     const { proxy } = await import('./proxy')
@@ -85,11 +85,11 @@ describe('marketplace proxy language bootstrap', () => {
     expect(response.cookies.set).not.toHaveBeenCalled()
   })
 
-  it('migrates the legacy marketplace language cookie into the shared cookie and request headers', async () => {
+  it('migrates the legacy storefront language cookie into the shared cookie and request headers', async () => {
     const { proxy } = await import('./proxy')
 
     const response = proxy(request({
-      cookies: { 'marketplace-language': 'ar' },
+      cookies: { 'storefront-language': 'ar' },
       headers: { cookie: 'session=abc' },
     }) as never) as any
 
@@ -118,7 +118,7 @@ describe('marketplace proxy language bootstrap', () => {
     const { proxy } = await import('./proxy')
 
     const response = proxy(request({
-      cookies: { 'rentaldrivego-language': 'es', 'marketplace-language': 'it' },
+      cookies: { 'rentaldrivego-language': 'es', 'storefront-language': 'it' },
       headers: { 'accept-language': 'fr-CA,ar;q=0.5' },
     }) as never) as any
 
@@ -127,7 +127,7 @@ describe('marketplace proxy language bootstrap', () => {
   })
 })
 
-describe('marketplace middleware dashboard path canonicalization', () => {
+describe('storefront middleware dashboard path canonicalization', () => {
   it('redirects duplicate dashboard prefixes to the clean dashboard URL', async () => {
     const { proxy } = await import('./proxy')