Add shop, POS sync, event ticketing, and shipping catalog apps.

Clients can run in-house retail without Shopify while keeping the same
Docker/Django/Postgres stack and data-ownership promise. Closes #5.

README.md

@@ -23,6 +23,10 @@ separate Django apps. A flag that is off keeps the app out of
 | Payments (Stripe) | `FEATURE_PAYMENTS` | `payments` (requires email/SMS) |
 | Social consolidation | `FEATURE_SOCIAL` | `social` |
 | AI social generator | `FEATURE_SOCIAL_AI` | `social_ai` (requires social) |
+| E-commerce storefront | `FEATURE_SHOP` | `shop` (requires email/SMS + payments) |
+| POS API sync | `FEATURE_POS_SYNC` | `pos_sync` (requires shop) |
+| Event ticketing | `FEATURE_EVENTS` | `events` (requires email/SMS + payments) |
+| Shipping automation | `FEATURE_SHIPPING` | `shipping` (requires shop) |
 
 ## New client