feat: 移除PDI和订单号字段，新增设备巡检模块

- 从物料跟踪页面移除订单号列和表单字段
- 从导航菜单移除PDI管理，添加设备巡检
- 新增InspectionLocation和InspectionRecord后端模型和API
- 新增设备巡检前端页面（左侧点位列表，右侧设备和历史记录）

backend/app/models/downtime.py

@@ -0,0 +1,38 @@
+from sqlalchemy import Column, Integer, String, Float, DateTime, Text, ForeignKey, func
+from app.database import Base
+
+
+class DowntimeCategory(Base):
+    """停机类别"""
+    __tablename__ = "downtime_categories"
+
+    id = Column(Integer, primary_key=True, index=True)
+    code = Column(String(20), unique=True, nullable=False)
+    name = Column(String(50), nullable=False)
+    category = Column(String(20), comment="大类: equipment/process/material/other")
+    description = Column(Text)
+    is_active = Column(Integer, default=1)
+
+
+class DowntimeRecord(Base):
+    """停机记录"""
+    __tablename__ = "downtime_records"
+
+    id = Column(Integer, primary_key=True, index=True)
+    category_id = Column(Integer, ForeignKey("downtime_categories.id"))
+    category_code = Column(String(20), index=True)
+    category_name = Column(String(50))
+    shift = Column(String(10), comment="班次")
+    shift_date = Column(DateTime, comment="班期")
+    start_time = Column(DateTime, nullable=False, comment="停机开始时间")
+    end_time = Column(DateTime, comment="停机结束时间")
+    duration = Column(Float, comment="停机时长min（自动计算）")
+    equipment_code = Column(String(30), comment="停机设备编号")
+    fault_desc = Column(Text, comment="故障描述")
+    action_taken = Column(Text, comment="处理措施")
+    root_cause = Column(Text, comment="根本原因")
+    reporter = Column(String(50), comment="报告人")
+    handler = Column(String(50), comment="处理人")
+    is_planned = Column(Integer, default=0, comment="是否计划停机")
+    created_at = Column(DateTime, server_default=func.now())
+    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now())