feat: add OMS platform admin and align "Store panel" naming

Add create_oms_admin (admin@omsflow.lu) alongside existing loyalty admin,
both using a shared create_platform_admin helper. Rename "Dashboard" and
"Staff login" labels to "Store panel" and "Store login" across seed output.
Add customer login URLs to production-style access section.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/seed/seed_demo.py

@@ -1379,10 +1379,10 @@ def print_summary(db: Session):
         if merchant and merchant.stores:
             for store in merchant.stores:
                 print(
-                    f"    Store:   http://localhost:8000/store/{store.store_code}/login"
+                    f"    Store panel: {base}/store/{store.store_code}/login"
                 )
                 print(
-                    f"           or http://{store.subdomain}.localhost:8000/store/login"  # noqa: SEC034
+                    f"              or http://{store.subdomain}.localhost:{port}/store/login"  # noqa: SEC034
                 )
         print()
 
@@ -1450,8 +1450,8 @@ def print_summary(db: Session):
             for pc in platform_codes:
                 print(f"    [{pc}] Storefront:      {base}/platforms/{pc}/storefront/{store.store_code}/")
                 print(f"    [{pc}] Customer login:  {base}/platforms/{pc}/storefront/{store.store_code}/account/login")
-                print(f"    [{pc}] Store dashboard: {base}/platforms/{pc}/store/{store.store_code}/")
-                print(f"    [{pc}] Staff login:     {base}/platforms/{pc}/store/{store.store_code}/login")
+                print(f"    [{pc}] Store panel:     {base}/platforms/{pc}/store/{store.store_code}/")
+                print(f"    [{pc}] Store login:     {base}/platforms/{pc}/store/{store.store_code}/login")
         else:
             print("    (!) No platform assigned")
 
@@ -1464,8 +1464,9 @@ def print_summary(db: Session):
             subdomain = d["custom_subdomain"] or store.subdomain
             pdomain = d["domain"] or f"{d['code']}.example.com"
             suffix = " (custom subdomain)" if d["custom_subdomain"] else ""
-            print(f"    [{d['code']}] Storefront: https://{subdomain}.{pdomain}/{suffix}")
-            print(f"    [{d['code']}] Dashboard:  https://{subdomain}.{pdomain}/store/dashboard")
+            print(f"    [{d['code']}] Storefront:      https://{subdomain}.{pdomain}/{suffix}")
+            print(f"    [{d['code']}] Customer login:  https://{subdomain}.{pdomain}/account/login")
+            print(f"    [{d['code']}] Store panel:     https://{subdomain}.{pdomain}/store/")
         # Show custom domain if any
         custom_domain = (
             db.query(StoreDomain)