feat: implement hybrid image extraction and memory management

Backend:
- Add hybrid image extraction for Direct track (inline image blocks)
- Add render_inline_image_regions() fallback when OCR doesn't find images
- Add check_document_for_missing_images() for detecting missing images
- Add memory management system (MemoryGuard, ModelManager, ServicePool)
- Update pdf_generator_service to handle HYBRID processing track
- Add ElementType.LOGO for logo extraction

Frontend:
- Fix PDF viewer re-rendering issues with memoization
- Add TaskNotFound component and useTaskValidation hook
- Disable StrictMode due to react-pdf incompatibility
- Fix task detail and results page loading states

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/pages/ProcessingPage.tsx

@@ -1,26 +1,35 @@
-import { useEffect, useState } from 'react'
+import { useState, useEffect } from 'react'
 import { useNavigate } from 'react-router-dom'
 import { useTranslation } from 'react-i18next'
-import { useQuery, useMutation } from '@tanstack/react-query'
+import { useMutation } from '@tanstack/react-query'
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
 import { Progress } from '@/components/ui/progress'
 import { Button } from '@/components/ui/button'
 import { Badge } from '@/components/ui/badge'
 import { useToast } from '@/components/ui/toast'
-import { useUploadStore } from '@/store/uploadStore'
 import { apiClientV2 } from '@/services/apiV2'
 import { Play, CheckCircle, FileText, AlertCircle, Clock, Activity, Loader2 } from 'lucide-react'
 import PPStructureParams from '@/components/PPStructureParams'
+import TaskNotFound from '@/components/TaskNotFound'
+import { useTaskValidation } from '@/hooks/useTaskValidation'
 import type { PPStructureV3Params, ProcessingOptions } from '@/types/apiV2'
 
 export default function ProcessingPage() {
   const { t } = useTranslation()
   const navigate = useNavigate()
   const { toast } = useToast()
-  const { batchId } = useUploadStore()
 
-  // In V2, batchId is actually a task_id (string)
-  const taskId = batchId ? String(batchId) : null
+  // Use shared hook for task validation
+  const { taskId, taskDetail, isLoading: isValidating, isNotFound, clearAndReset } = useTaskValidation({
+    refetchInterval: (query) => {
+      const data = query.state.data
+      if (!data) return 2000
+      if (data.status === 'completed' || data.status === 'failed') {
+        return false
+      }
+      return 2000
+    },
+  })
 
   // PP-StructureV3 parameters state
   const [ppStructureParams, setPpStructureParams] = useState<PPStructureV3Params>({})
@@ -56,22 +65,6 @@ export default function ProcessingPage() {
     },
   })
 
-  // Poll task status
-  const { data: taskDetail } = useQuery({
-    queryKey: ['taskDetail', taskId],
-    queryFn: () => apiClientV2.getTask(taskId!),
-    enabled: !!taskId,
-    refetchInterval: (query) => {
-      const data = query.state.data
-      if (!data) return 2000
-      // Stop polling if completed or failed
-      if (data.status === 'completed' || data.status === 'failed') {
-        return false
-      }
-      return 2000 // Poll every 2 seconds
-    },
-  })
-
   // Auto-redirect when completed
   useEffect(() => {
     if (taskDetail?.status === 'completed') {
@@ -115,6 +108,23 @@ export default function ProcessingPage() {
     }
   }
 
+  // Show loading while validating task
+  if (isValidating) {
+    return (
+      <div className="flex items-center justify-center min-h-[60vh]">
+        <div className="text-center">
+          <Loader2 className="w-12 h-12 animate-spin text-primary mx-auto mb-4" />
+          <p className="text-muted-foreground">載入任務資訊...</p>
+        </div>
+      </div>
+    )
+  }
+
+  // Show message when task was deleted
+  if (isNotFound) {
+    return <TaskNotFound taskId={taskId} onClearAndUpload={clearAndReset} />
+  }
+
   // Show helpful message when no task is selected
   if (!taskId) {
     return (