feat(sync): add order_total field to SQLite tracking

Parse order total from GoMag JSON, store in SQLite orders table,
and expose via sync run API. Enables total display in mobile flat rows.

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

api/app/services/order_reader.py

@@ -54,6 +54,7 @@ class OrderData:
     items: list = field(default_factory=list)  # list of OrderItem
     billing: OrderBilling = field(default_factory=OrderBilling)
     shipping: Optional[OrderShipping] = None
+    total: float = 0.0
     payment_name: str = ""
     delivery_name: str = ""
     source_file: str = ""
@@ -163,6 +164,7 @@ def _parse_order(order_id: str, data: dict, source_file: str) -> OrderData:
         items=items,
         billing=billing,
         shipping=shipping,
+        total=float(data.get("total", 0) or 0),
         payment_name=str(payment.get("name", "")) if isinstance(payment, dict) else "",
         delivery_name=str(delivery.get("name", "")) if isinstance(delivery, dict) else "",
         source_file=source_file