feat: add pre/post-tax price linkage, hide barcode, and tablet adapt

Co-authored-by: aider (openai/DeepSeek-V3.2-Thinking) <aider@aider.chat>

inventory-backend/app/models/inbound/buy.py

@@ -34,6 +34,7 @@ class StockBuy(db.Model):
 
     # 财务与商务
     unit_price = db.Column(db.Numeric(19, 4), default=0)  # 现意为：不含税单价
+    post_tax_unit_price = db.Column(db.Numeric(19, 4), default=0)  # 税后单价
     total_price = db.Column(db.Numeric(19, 4), default=0)  # 总价
     # [新增] 税率
     tax_rate = db.Column(db.Numeric(5, 2), default=0)
@@ -98,6 +99,7 @@ class StockBuy(db.Model):
             'qty_available': float(self.available_quantity or 0),
 
             'unit_price': float(self.unit_price or 0),
+            'post_tax_unit_price': float(self.post_tax_unit_price or 0),
             'total_price': float(self.total_price or 0),
             # [新增] 税率
             'tax_rate': float(self.tax_rate or 0),
@@ -116,4 +118,4 @@ class StockBuy(db.Model):
 
             'global_print_id': self.global_print_id,
             'global_print_id_str': f"{self.global_print_id:010d}" if self.global_print_id else ""
-        }
+        }