fix(critical): SQLAlchemy mapper crash + material matching for USD renders + kanban drag-to-reject

- beat_tasks.py: import app.models at module level so SQLAlchemy can
  resolve relationship("Template") and relationship("User") when domain
  models are imported in isolation inside task functions. Fixes all
  beat tasks (batch_render_notifications, recover_stuck_cad_files) that
  crashed every 60s with mapper initialization error.

- _blender_materials.py: build_mat_map_lower() now adds a slug-normalized
  key variant (re.sub([^a-z0-9]+, _, kl)) for each mat_map entry. OCC
  part names like 'F-802007_TR4-D1-H122AG' → slug 'f_802007_tr4_d1_h122ag'
  now matches USD-imported Blender objects. Existing prefix fallback
  (key.startswith(part_key)) catches AF-suffix variants.

- Orders.tsx: kanban drag-to-reject implemented. submitted/processing
  cards are draggable (cursor-grab). Rejected column highlights with
  red ring on drag-over. Drop opens reject reason modal via createPortal.
  Confirm calls rejectOrder() mutation + invalidates orders cache.

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

frontend/src/pages/Orders.tsx

@@ -1,6 +1,7 @@
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import { Link, useNavigate } from 'react-router-dom'
-import { useState, useMemo, useEffect } from 'react'
+import { useState, useMemo, useEffect, useRef } from 'react'
+import { createPortal } from 'react-dom'
 import {
   Plus, Package, Trash2, X, Search, SlidersHorizontal,
   LayoutGrid, LayoutList, Calendar, FileSpreadsheet,
@@ -8,7 +9,7 @@ import {
   ChevronRight, Filter,
 } from 'lucide-react'
 import { toast } from 'sonner'
-import { listOrders, searchOrders, deleteOrder } from '../api/orders'
+import { listOrders, searchOrders, deleteOrder, rejectOrder } from '../api/orders'
 import { fetchThumbnailBlob } from '../api/cad'
 import type { Order, OrderDetail, OrderItem } from '../api/orders'
 import ConfirmModal from '../components/ConfirmModal'
@@ -51,6 +52,9 @@ export default function OrdersPage() {
   const [showFilters, setShowFilters] = useState(false)
   const [selected, setSelected] = useState<Set<string>>(new Set())
   const [confirmState, setConfirmState] = useState<{ open: boolean; title: string; message: string; onConfirm: () => void }>({ open: false, title: '', message: '', onConfirm: () => {} })
+  const [dragRejectOpen, setDragRejectOpen] = useState(false)
+  const [dragRejectReason, setDragRejectReason] = useState('')
+  const pendingRejectIdRef = useRef<string | null>(null)
 
   // Auto-switch to list view on narrow screens
   useEffect(() => {
@@ -167,6 +171,25 @@ export default function OrdersPage() {
     onError: (e: any) => toast.error(e.response?.data?.detail || 'Delete failed'),
   })
 
+  const rejectOrderMut = useMutation({
+    mutationFn: ({ id, reason }: { id: string; reason: string }) =>
+      rejectOrder(id, reason),
+    onSuccess: () => {
+      toast.success('Order rejected')
+      setDragRejectOpen(false)
+      setDragRejectReason('')
+      pendingRejectIdRef.current = null
+      qc.invalidateQueries({ queryKey: ['orders'] })
+    },
+    onError: (e: any) => toast.error(e.response?.data?.detail || 'Reject failed'),
+  })
+
+  const handleDropReject = (orderId: string) => {
+    pendingRejectIdRef.current = orderId
+    setDragRejectReason('')
+    setDragRejectOpen(true)
+  }
+
   const handleDeleteSelected = () => {
     const ids = [...selected]
     if (!ids.length) return
@@ -362,6 +385,7 @@ export default function OrdersPage() {
           byStatus={byStatus}
           visibleStatuses={visibleStatuses}
           onNavigate={(id) => navigate(`/orders/${id}`)}
+          onDropReject={handleDropReject}
         />
       ) : (
         <ListView
@@ -382,6 +406,52 @@ export default function OrdersPage() {
         onCancel={() => setConfirmState((s) => ({ ...s, open: false }))}
       />
 
+      {dragRejectOpen && createPortal(
+        <div
+          className="fixed inset-0 z-50 flex items-center justify-center bg-black/50"
+          onClick={(e) => { if (e.target === e.currentTarget) setDragRejectOpen(false) }}
+        >
+          <div className="bg-surface rounded-xl shadow-xl p-6 w-full max-w-sm mx-4 space-y-4">
+            <div className="flex items-center justify-between">
+              <h2 className="font-semibold text-content">Reject Order</h2>
+              <button onClick={() => setDragRejectOpen(false)} className="text-content-muted hover:text-content">
+                <X size={18} />
+              </button>
+            </div>
+            <p className="text-sm text-content-secondary">Optionally add a rejection reason:</p>
+            <textarea
+              className="w-full border border-border-default rounded-lg px-3 py-2 text-sm bg-surface-muted text-content resize-none focus:outline-none focus:ring-2 focus:ring-accent"
+              rows={3}
+              placeholder="Reason (optional)"
+              value={dragRejectReason}
+              onChange={(e) => setDragRejectReason(e.target.value)}
+              autoFocus
+            />
+            <div className="flex gap-2 justify-end">
+              <button
+                onClick={() => setDragRejectOpen(false)}
+                className="btn-secondary text-sm"
+              >
+                Cancel
+              </button>
+              <button
+                onClick={() => {
+                  if (pendingRejectIdRef.current) {
+                    rejectOrderMut.mutate({ id: pendingRejectIdRef.current, reason: dragRejectReason })
+                  }
+                }}
+                disabled={rejectOrderMut.isPending}
+                className="btn-danger text-sm"
+              >
+                {rejectOrderMut.isPending ? <Loader2 size={14} className="animate-spin" /> : <XCircle size={14} />}
+                Reject Order
+              </button>
+            </div>
+          </div>
+        </div>,
+        document.body
+      )}
+
       {/* ── Bulk delete bar ───────────────────────────────────────────────── */}
       {selected.size > 0 && (
         <div
@@ -677,19 +747,35 @@ function KanbanBoard({
   byStatus,
   visibleStatuses,
   onNavigate,
+  onDropReject,
 }: {
   byStatus: Record<Status, Order[]>
   visibleStatuses: Status[]
   onNavigate: (id: string) => void
+  onDropReject?: (orderId: string) => void
 }) {
+  const [dragOverRejected, setDragOverRejected] = useState(false)
+
   return (
     <div className="flex-1 overflow-x-auto min-h-0">
       <div className="flex gap-4 p-6 h-full min-w-max">
         {visibleStatuses.map((status) => {
           const meta = STATUS_META[status]
           const cards = byStatus[status]
+          const isRejectedCol = status === 'rejected'
           return (
-            <div key={status} className="flex flex-col w-72 min-w-[272px]">
+            <div
+              key={status}
+              className={`flex flex-col w-72 min-w-[272px] ${isRejectedCol && dragOverRejected ? 'ring-2 ring-red-400 rounded-xl' : ''}`}
+              onDragOver={isRejectedCol ? (e) => { e.preventDefault(); setDragOverRejected(true) } : undefined}
+              onDragLeave={isRejectedCol ? () => setDragOverRejected(false) : undefined}
+              onDrop={isRejectedCol ? (e) => {
+                e.preventDefault()
+                setDragOverRejected(false)
+                const orderId = e.dataTransfer.getData('orderId')
+                if (orderId && onDropReject) onDropReject(orderId)
+              } : undefined}
+            >
               <div className={`${meta.header} rounded-t-xl px-4 py-3 flex items-center gap-2`}>
                 <meta.icon size={16} className="text-white/80 shrink-0" />
                 <span className="text-white font-semibold text-sm">{meta.label}</span>
@@ -697,10 +783,10 @@ function KanbanBoard({
                   {cards.length}
                 </span>
               </div>
-              <div className="flex-1 bg-surface-muted rounded-b-xl p-2 overflow-y-auto space-y-2 min-h-[120px]">
+              <div className={`flex-1 bg-surface-muted rounded-b-xl p-2 overflow-y-auto space-y-2 min-h-[120px] ${isRejectedCol && dragOverRejected ? 'bg-red-50' : ''}`}>
                 {cards.length === 0 ? (
-                  <div className="h-20 flex items-center justify-center text-content-muted text-xs">
-                    No orders
+                  <div className={`h-20 flex items-center justify-center text-xs ${isRejectedCol && dragOverRejected ? 'text-red-400 font-medium' : 'text-content-muted'}`}>
+                    {isRejectedCol && dragOverRejected ? 'Drop to reject' : 'No orders'}
                   </div>
                 ) : (
                   cards.map((order) => (
@@ -762,12 +848,19 @@ function KanbanCard({
 
   const rp = order.render_progress
 
+  const isDraggable = order.status === 'submitted' || order.status === 'processing'
+
   return (
     <button
       onClick={onNavigate}
+      draggable={isDraggable}
+      onDragStart={isDraggable ? (e) => {
+        e.dataTransfer.setData('orderId', order.id)
+        e.dataTransfer.effectAllowed = 'move'
+      } : undefined}
       className={`w-full text-left bg-surface rounded-lg shadow-sm border border-border-default
                   border-l-4 ${meta.card} hover:shadow-md hover:-translate-y-0.5
-                  transition-all duration-150 p-3 group`}
+                  transition-all duration-150 p-3 group ${isDraggable ? 'cursor-grab active:cursor-grabbing' : ''}`}
     >
       <div className="flex items-start justify-between gap-2 mb-2">
         <span className="text-sm font-bold text-content font-mono leading-tight">