Add shop, POS sync, event ticketing, and shipping catalog apps (#6)

## Summary
- Closes #5
- Optional `shop`, `pos_sync`, `events`, and `shipping` apps gated by `FEATURE_*` flags
- Deps match the catalog: shop/events need email + Stripe; POS/shipping need shop
- Portal inventory, POS webhooks, capacity tickets, EasyPost/Pirate Ship shipping

## Test plan
- [ ] `manage.py test` (152 passed locally)
- [ ] Shop cart + paid order decrements stocked inventory
- [ ] POS inbound webhook decrements SKU; paid order queues outbound reserve
- [ ] Event capacity blocks overbook; paid order emails ticket codes
- [ ] Shipping stub label + Pirate Ship CSV of unshipped paid orders
- [ ] `validate-env.sh` rejects shop without email/payments, POS/shipping without shop

Reviewed-on: #6

site/core/registry.py

@@ -22,6 +22,7 @@ GROUP_ORDER = {
     "Outreach": 20,
     "Content": 30,
     "Social": 40,
+    "Retail": 45,
     "Billing": 50,
 }
 

site/core/tests_features.py

@@ -22,16 +22,30 @@ class FeatureFlagSettingsTests(SimpleTestCase):
         self.assertIn("FEATURE_PAYMENTS", src)
         self.assertIn("FEATURE_SOCIAL", src)
         self.assertIn("FEATURE_SOCIAL_AI", src)
+        self.assertIn("FEATURE_SHOP", src)
+        self.assertIn("FEATURE_POS_SYNC", src)
+        self.assertIn("FEATURE_EVENTS", src)
+        self.assertIn("FEATURE_SHIPPING", src)
         self.assertIn("email_sms.apps.EmailSmsConfig", src)
         self.assertIn("directmail.apps.DirectmailConfig", src)
         self.assertIn("blog.apps.BlogConfig", src)
         self.assertIn("payments.apps.PaymentsConfig", src)
         self.assertIn("social_ai.apps.SocialAiConfig", src)
+        self.assertIn("shop.apps.ShopConfig", src)
+        self.assertIn("pos_sync.apps.PosSyncConfig", src)
+        self.assertIn("events.apps.EventsConfig", src)
+        self.assertIn("shipping.apps.ShippingConfig", src)
 
     def test_payments_requires_email_sms_in_source(self):
         src = _read_settings_source()
         self.assertIn("FEATURE_PAYMENTS requires FEATURE_EMAIL_SMS", src)
         self.assertIn("FEATURE_SOCIAL_AI requires FEATURE_SOCIAL", src)
+        self.assertIn("FEATURE_SHOP requires FEATURE_EMAIL_SMS", src)
+        self.assertIn("FEATURE_SHOP requires FEATURE_PAYMENTS", src)
+        self.assertIn("FEATURE_POS_SYNC requires FEATURE_SHOP", src)
+        self.assertIn("FEATURE_EVENTS requires FEATURE_EMAIL_SMS", src)
+        self.assertIn("FEATURE_EVENTS requires FEATURE_PAYMENTS", src)
+        self.assertIn("FEATURE_SHIPPING requires FEATURE_SHOP", src)
 
 
 class AlwaysOnImportIsolationTests(SimpleTestCase):
@@ -44,6 +58,10 @@ class AlwaysOnImportIsolationTests(SimpleTestCase):
         "payments",
         "social",
         "social_ai",
+        "shop",
+        "pos_sync",
+        "events",
+        "shipping",
     }
 
     ALWAYS_ON = [
@@ -82,7 +100,18 @@ class InstalledOptionalAppsTests(TestCase):
 
     def test_dev_installs_catalog_apps(self):
         labels = {c.label for c in apps.get_app_configs()}
-        for label in ("email_sms", "directmail", "blog", "payments", "social", "social_ai"):
+        for label in (
+            "email_sms",
+            "directmail",
+            "blog",
+            "payments",
+            "social",
+            "social_ai",
+            "shop",
+            "pos_sync",
+            "events",
+            "shipping",
+        ):
             self.assertIn(label, labels)
 
     def test_optional_urls_resolve_when_installed(self):
@@ -92,3 +121,10 @@ class InstalledOptionalAppsTests(TestCase):
         self.assertTrue(reverse("payments:invoice_list").startswith("/portal/payments/"))
         self.assertTrue(reverse("social:composer").startswith("/portal/social/"))
         self.assertTrue(reverse("social_ai:generate").startswith("/portal/social/api/generate/"))
+        self.assertTrue(reverse("shop:list").startswith("/shop/"))
+        self.assertTrue(reverse("shop_portal:product_list").startswith("/portal/shop/"))
+        self.assertTrue(reverse("shop_portal:sales").startswith("/portal/shop/sales/"))
+        self.assertTrue(reverse("pos_sync:event_list").startswith("/portal/pos/"))
+        self.assertTrue(reverse("events:list").startswith("/events/"))
+        self.assertTrue(reverse("events_portal:event_list").startswith("/portal/events/"))
+        self.assertTrue(reverse("shipping:shipment_list").startswith("/portal/shipping/"))