fix(loyalty): read Google Wallet config from core settings instead of module config

Module config only reads from os.environ (not .env), so wallet settings
were always None. Core Settings already loads these via env_file=".env".
Also adds comprehensive wallet creation tests with mocked Google API.

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

app/modules/loyalty/schemas/card.py

@@ -175,6 +175,9 @@ class TransactionResponse(BaseModel):
     reward_description: str | None = None
     notes: str | None = None
 
+    # Customer
+    customer_name: str | None = None
+
     # Staff
     staff_name: str | None = None