feat(price): detect quantity discounts via baseprice, show Disc. badge

GoMag sends baseprice (catalog price) alongside price (discounted).
When baseprice > price, the item is volume-discounted — skip ROA
price comparison and show amber "Disc." badge instead of false
mismatch. Strikethrough baseprice in price column for transparency.

Pipeline: parse baseprice → store in SQLite → skip in validation →
pass flag to frontend → render badge (desktop + mobile pill badge
with aria-label, opacity 0.6 for dark mode).

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

api/app/services/order_reader.py

@@ -17,6 +17,7 @@ class OrderItem:
     price: float
     quantity: float
     vat: float
+    baseprice: float = 0.0
 
 @dataclass
 class OrderBilling:
@@ -116,7 +117,8 @@ def _parse_order(order_id: str, data: dict, source_file: str) -> OrderData:
                     name=str(item.get("name", "")),
                     price=float(item.get("price", 0) or 0),
                     quantity=float(item.get("quantity", 0) or 0),
-                    vat=float(item.get("vat", 0) or 0)
+                    vat=float(item.get("vat", 0) or 0),
+                    baseprice=float(item.get("baseprice", 0) or 0)
                 ))
 
     # Parse billing