fix(tenancy): use is_production() for invitation URL instead of debug flag

Using debug flag for environment detection is unreliable — if left
True in prod, links would point to localhost. Now uses the proper
is_production() from environment module.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/tenancy/services/store_team_service.py

@@ -981,18 +981,17 @@ class StoreTeamService:
     ):
         """Send team invitation email."""
         from app.core.config import settings as app_settings
+        from app.core.environment import is_production
         from app.modules.messaging.services.email_service import EmailService
 
-        # Build acceptance URL using store's subdomain or main domain
-        store_subdomain = store.subdomain
+        # Build acceptance URL
+        # Prod: https://{subdomain}.{main_domain}/invitation/accept?token=...
+        # Dev:  http://localhost:8000/store/{store_code}/invitation/accept?token=...
         main_domain = app_settings.main_domain.rstrip("/")
-
-        if app_settings.debug or "localhost" in main_domain:
-            # Dev: use localhost with store path
-            base_url = f"http://localhost:8000/store/{store.store_code}"
+        if is_production():
+            base_url = f"https://{store.subdomain}.{main_domain}"
         else:
-            # Prod: use store subdomain
-            base_url = f"https://{store_subdomain}.{main_domain}"
+            base_url = f"http://localhost:8000/store/{store.store_code}"
 
         acceptance_link = f"{base_url}/invitation/accept?token={token}"