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/equipment.py

@@ -0,0 +1,53 @@
+from sqlalchemy import Column, Integer, String, Float, DateTime, Enum, Text, ForeignKey, func
+from app.database import Base
+import enum
+
+
+class EquipmentStatus(str, enum.Enum):
+    NORMAL = "normal"       # 正常
+    FAULT = "fault"         # 故障
+    MAINTENANCE = "maintenance"  # 检修
+    STANDBY = "standby"     # 备用
+
+
+class Equipment(Base):
+    """设备台账"""
+    __tablename__ = "equipments"
+
+    id = Column(Integer, primary_key=True, index=True)
+    code = Column(String(30), unique=True, nullable=False, index=True, comment="设备编号")
+    name = Column(String(100), nullable=False, comment="设备名称")
+    category = Column(String(30), comment="设备类别")
+    model = Column(String(50), comment="型号规格")
+    manufacturer = Column(String(100), comment="制造厂商")
+    install_date = Column(DateTime, comment="投用日期")
+    location = Column(String(50), comment="安装位置")
+    status = Column(Enum(EquipmentStatus), default=EquipmentStatus.NORMAL)
+    rated_power = Column(Float, comment="额定功率kW")
+    remark = Column(Text)
+    created_at = Column(DateTime, server_default=func.now())
+    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now())
+
+
+class EquipmentMaintenance(Base):
+    """设备维保记录"""
+    __tablename__ = "equipment_maintenance"
+
+    id = Column(Integer, primary_key=True, index=True)
+    equipment_id = Column(Integer, ForeignKey("equipments.id"), nullable=False)
+    equipment_code = Column(String(30), index=True)
+    maintenance_type = Column(String(20), comment="类型: repair/planned/inspection")
+    title = Column(String(200), nullable=False)
+    description = Column(Text, comment="维保内容")
+    start_time = Column(DateTime, nullable=False)
+    end_time = Column(DateTime)
+    duration = Column(Float, comment="工时h")
+    cost = Column(Float, comment="费用元")
+    spare_parts = Column(Text, comment="更换备件（JSON格式）")
+    technician = Column(String(50), comment="执行人")
+    approver = Column(String(50), comment="审核人")
+    next_maintenance = Column(DateTime, comment="下次维保时间")
+    result = Column(String(20), comment="结果: pass/fail/pending")
+    remark = Column(Text)
+    created_at = Column(DateTime, server_default=func.now())
+    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now())