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/lib/appUrls.test.ts

@@ -12,7 +12,7 @@ afterEach(() => {
   Reflect.deleteProperty(globalThis, 'window')
 })
 
-describe('marketplace app URL resolution', () => {
+describe('storefront app URL resolution', () => {
   it('leaves server-side browser fallback unchanged when window is unavailable', () => {
     expect(resolveBrowserAppUrl('http://localhost:3000')).toBe('http://localhost:3000')
   })
@@ -29,7 +29,7 @@ describe('marketplace app URL resolution', () => {
 
   it('keeps path prefixes while rewriting the browser origin', () => {
     installWindow('rental.example.com', 'https:')
-    expect(resolveBrowserAppUrl('http://localhost:3000/marketplace')).toBe('https://rental.example.com/marketplace')
+    expect(resolveBrowserAppUrl('http://localhost:3000/storefront')).toBe('https://rental.example.com/storefront')
   })
 
   it('resolves server URLs from forwarded host/proto and handles invalid fallbacks safely', () => {