feat: add boxing module API — GET /box/info and POST /box

- Add box schemas (BoxInfoResponse, BoxSaveRequest, BoxSaveResponse)
- Add box service with ERP view query and save logic (supports many2one append)
- Add box router with GET /box/info and POST /box endpoints
- Register exception handlers for InvalidZongpaiError, ZongpaiNotFoundError, DuplicateBoxItemError
- Update RequestValidationError handler to cover INVALID_BOX_NO and INVALID_QUANTITY
- Add 7 integration tests for box API

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

app/schemas/box.py

@@ -0,0 +1,65 @@
+import re
+
+from pydantic import BaseModel, field_validator
+
+ZONGPAI_PATTERN = re.compile(r"^(\d{2}(B|C|T)\d+|\d{2}(BW|CW)\d{4})$")
+
+
+class BoxItemDetail(BaseModel):
+    """箱号下某个总排号的明细"""
+    zongpai_no: str
+    quantity: int
+
+
+class BoxDetail(BaseModel):
+    """一个箱号的完整信息"""
+    box_no: int
+    items: list[BoxItemDetail]
+
+
+class BoxInfoResponse(BaseModel):
+    """GET /box/info 响应"""
+    zongpai_no: str
+    paichan_no: str
+    quantity: int
+    existing_boxes: list[BoxDetail]
+    max_box_no: int
+    suggested_box_no: int
+
+
+class BoxSaveRequest(BaseModel):
+    """POST /box 请求"""
+    zongpai_no: str
+    box_no: int
+    quantity: int
+
+    @field_validator("zongpai_no")
+    @classmethod
+    def validate_zongpai_no(cls, v: str) -> str:
+        v = v.strip().upper()
+        if not ZONGPAI_PATTERN.match(v):
+            raise ValueError("INVALID_ZONGPAI")
+        return v
+
+    @field_validator("box_no")
+    @classmethod
+    def validate_box_no(cls, v: int) -> int:
+        if v <= 0:
+            raise ValueError("INVALID_BOX_NO")
+        return v
+
+    @field_validator("quantity")
+    @classmethod
+    def validate_quantity(cls, v: int) -> int:
+        if v <= 0:
+            raise ValueError("INVALID_QUANTITY")
+        return v
+
+
+class BoxSaveResponse(BaseModel):
+    """POST /box 响应"""
+    paichan_no: str
+    box_no: int
+    zongpai_no: str
+    quantity: int
+    created_at: str