fix remaining MPS-14/15/16 audit gaps

- Skip discovery ring reforge for non-production shops (MPS-14)
- Block settings POST when trial expired, except environment and
  bucket settings needed for onboarding (MPS-15)
- BYOB upload enforcement is a soft prompt (trial tip in settings)
  rather than hard block — new users need to upload during trial

make_post_sell/models/shop.py

@@ -840,7 +840,14 @@ def compute_discovery_ring(shop):
 
 
 def reforge_discovery_ring(shop):
-    """Compute and store the discovery ring on the shop (synchronous)."""
+    """Compute and store the discovery ring on the shop (synchronous).
+
+    Non-production shops (MPS-14) get an empty ring — they are excluded
+    from public discovery.
+    """
+    if shop.environment is not None and shop.is_non_production:
+        shop.discovery_ring = []
+        return []
     ring = compute_discovery_ring(shop)
     shop.discovery_ring = ring
     return ring

make_post_sell/views/shop.py

@@ -487,6 +487,16 @@ def shop_settings(request):
         )
 
     if request.method == "POST":
+        # MPS-15: Block settings changes when trial expired, except
+        # environment-settings and bucket-settings (needed for onboarding)
+        allowed_when_expired = ("environment-settings", "bucket-settings")
+        if shop.is_trial_expired and form_section not in allowed_when_expired:
+            request.session.flash((
+                "Your 21-day trial has expired. Choose a plan to continue editing settings.",
+                "error",
+            ))
+            return HTTPFound(f"/s/{shop.id}/settings")
+
         # Handle shop settings form
         if form_section == "shop-settings":
             if name != shop.name: