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/services/platformContentService.ts

@@ -1,6 +1,6 @@
 import { mkdir, readFile, writeFile } from 'fs/promises'
 import path from 'path'
-import { cloneMarketplaceHomepageContent, type MarketplaceHomepageConfig } from '@rentaldrivego/types'
+import { cloneStorefrontHomepageContent, type StorefrontHomepageConfig } from '@rentaldrivego/types'
 
 function resolveContentPath() {
   const cwd = process.cwd()
@@ -12,7 +12,7 @@ function resolveContentPath() {
 const platformContentPath = resolveContentPath()
 
 type PlatformContentFile = {
-  marketplaceHomepage?: MarketplaceHomepageConfig
+  storefrontHomepage?: StorefrontHomepageConfig
 }
 
 async function readPlatformContentFile(): Promise<PlatformContentFile> {
@@ -29,16 +29,16 @@ async function writePlatformContentFile(content: PlatformContentFile) {
   await writeFile(platformContentPath, JSON.stringify(content, null, 2))
 }
 
-export async function getMarketplaceHomepageContent() {
+export async function getStorefrontHomepageContent() {
   const content = await readPlatformContentFile()
-  return content.marketplaceHomepage ?? cloneMarketplaceHomepageContent()
+  return content.storefrontHomepage ?? cloneStorefrontHomepageContent()
 }
 
-export async function saveMarketplaceHomepageContent(homepage: MarketplaceHomepageConfig) {
+export async function saveStorefrontHomepageContent(homepage: StorefrontHomepageConfig) {
   const content = await readPlatformContentFile()
   await writePlatformContentFile({
     ...content,
-    marketplaceHomepage: homepage,
+    storefrontHomepage: homepage,
   })
   return homepage
 }