feat: restore marketplace edition

[roncodes]

Summary

• select single-store or marketplace mode from the typed owner returned by GET /storefront/v1/about
• add marketplace discovery, filters, categories, search, map/list browsing, merchant storefronts, and resilient category/product deep links
• namespace persisted state by host and hashed owner key without storing API-key material
• group carts by merchant, enforce single- versus multi-store policy, preserve delivery origins, and surface actionable checkout failures
• request location only for nearby/map actions and retain non-location browsing when permission is denied
• preserve the existing single-store edition, add English and Mongolian copy, responsive states, and CI gates

Validation

• yarn lint:marketplace
• yarn typecheck:marketplace
• yarn test:ci --watchman=false — 8/8 tests
• Android production JS bundle — succeeded
• iOS production JS bundle — succeeded
• yarn web:build — succeeded; existing React Native Web compatibility and bundle-size warnings remain

Cross-repository dependencies

Deploy the Storefront backend dev-v0.4.19 API and storefront-js feature/marketplace-sdk before releasing this app. The API-spec and docs branches are feature/marketplace-api-spec and feature/marketplace-docs.

Review focus

Please verify both store_... and network_... boot paths, cart replacement/multi-store behavior, authenticated checkout identity, payment gateways, location denial, and native deep links.