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

docs/project-design/FEATURES.md

@@ -4,7 +4,7 @@ This document lists the features that are active in the current codebase.
 
 Source of truth:
 
-- `apps/marketplace`
+- `apps/storefront`
 - `apps/dashboard`
 - `apps/admin`
 - `apps/api`
@@ -14,7 +14,7 @@ Source of truth:
 
 The current workspace contains four active apps:
 
-- `apps/marketplace`
+- `apps/storefront`
 - `apps/dashboard`
 - `apps/admin`
 - `apps/api`
@@ -61,12 +61,12 @@ There is no separate frontend app for a white-label company public site in this
 - Notification inbox and preferences
 - Subscription management
 
-### Marketplace and public platform
+### Storefront and public platform
 
 - Public marketing homepage
 - Public pricing page
 - Public features page
-- Public marketplace/explore flow
+- Public storefront/explore flow
 - Explore company profile pages under `/explore/[slug]`
 - Public review submission page via review token
 - Public legal/app policy pages
@@ -120,7 +120,7 @@ There is no separate frontend app for a white-label company public site in this
 - Billing operations
 - Pricing configuration and promotions
 - Notification review
-- Marketplace/site config management
+- Storefront/site config management
 
 ## Present But Not Active Product Features
 
@@ -144,9 +144,9 @@ The following old design ideas should not be treated as active features unless c
 - standalone about/contact page set
 - Google renter auth
 - automatic custom-domain provisioning
-- Zapier/webhook marketplace integrations beyond the current API/webhook handlers
+- Zapier/webhook storefront integrations beyond the current API/webhook handlers
 
 ## Notes
 
 - The database still contains legacy fields such as `Employee.clerkUserId`, but those fields are no longer evidence of active Clerk integration.
-- Some renter-facing `/renter/*` pages exist in the marketplace app, but the auth entrypoints they depend on are not active. They are therefore not listed as active product scope here.
+- Some renter-facing `/renter/*` pages exist in the storefront app, but the auth entrypoints they depend on are not active. They are therefore not listed as active product scope here.