refactor: rename platform_domain → main_domain to avoid confusion with platform.domain

The setting `settings.platform_domain` (the global/main domain like "wizard.lu")
was easily confused with `platform.domain` (per-platform domain like "rewardflow.lu").
Renamed to `settings.main_domain` / `MAIN_DOMAIN` env var across the entire codebase.

Also updated docs to reflect the refactored store detection logic with
`is_platform_domain` / `is_subdomain_of_platform` guards.

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

scripts/seed/init_production.py

@@ -390,14 +390,14 @@ def create_admin_settings(db: Session) -> int:
         },
         {
             "key": "platform_url",
-            "value": f"https://{settings.platform_domain}",
+            "value": f"https://{settings.main_domain}",
             "value_type": "string",
             "description": "Main platform URL",
             "is_public": True,
         },
         {
             "key": "support_email",
-            "value": f"support@{settings.platform_domain}",
+            "value": f"support@{settings.main_domain}",
             "value_type": "string",
             "description": "Platform support email",
             "is_public": True,

scripts/seed/install.py

@@ -339,7 +339,7 @@ def validate_configuration(env_vars: dict) -> dict:
     # -------------------------------------------------------------------------
     # Platform Domain
     # -------------------------------------------------------------------------
-    domain = env_vars.get("PLATFORM_DOMAIN", "orion.lu")
+    domain = env_vars.get("MAIN_DOMAIN", "orion.lu")
     if domain != "orion.lu":
         results["domain"] = {
             "status": "ok",
@@ -350,7 +350,7 @@ def validate_configuration(env_vars: dict) -> dict:
         results["domain"] = {
             "status": "warning",
             "message": "Using default domain",
-            "items": ["Set PLATFORM_DOMAIN for your deployment"]
+            "items": ["Set MAIN_DOMAIN for your deployment"]
         }
 
     # -------------------------------------------------------------------------

scripts/seed/seed_demo.py

@@ -1445,7 +1445,7 @@ def print_summary(db: Session):
     print("\n🏪 Demo Stores:")
     for store in stores:
         print(f"\n  {store.name} ({store.store_code})")
-        print(f"    Subdomain: {store.subdomain}.{settings.platform_domain}")
+        print(f"    Subdomain: {store.subdomain}.{settings.main_domain}")
 
         # Show per-platform custom subdomains
         from app.modules.tenancy.models import Platform