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/ResultsPage.tsx

@@ -1,29 +1,23 @@
+import { useMemo } from 'react'
 import { useNavigate } from 'react-router-dom'
 import { useTranslation } from 'react-i18next'
-import { useQuery } from '@tanstack/react-query'
 import { Button } from '@/components/ui/button'
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
 import PDFViewer from '@/components/PDFViewer'
 import { useToast } from '@/components/ui/toast'
-import { useUploadStore } from '@/store/uploadStore'
 import { apiClientV2 } from '@/services/apiV2'
 import { FileText, Download, AlertCircle, TrendingUp, Clock, Layers, FileJson, Loader2 } from 'lucide-react'
 import { Badge } from '@/components/ui/badge'
+import TaskNotFound from '@/components/TaskNotFound'
+import { useTaskValidation } from '@/hooks/useTaskValidation'
 
 export default function ResultsPage() {
   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
-
-  // Get task details
-  const { data: taskDetail, isLoading } = useQuery({
-    queryKey: ['taskDetail', taskId],
-    queryFn: () => apiClientV2.getTask(taskId!),
-    enabled: !!taskId,
+  // Use shared hook for task validation
+  const { taskId, taskDetail, isLoading, isNotFound, clearAndReset } = useTaskValidation({
     refetchInterval: (query) => {
       const data = query.state.data
       if (!data) return 2000
@@ -34,6 +28,19 @@ export default function ResultsPage() {
     },
   })
 
+  // Construct PDF URL for preview - memoize to prevent unnecessary reloads
+  // Must be called unconditionally before any early returns (React hooks rule)
+  const API_BASE_URL = import.meta.env.VITE_API_BASE_URL || 'http://localhost:8000'
+  const pdfUrl = useMemo(() => {
+    return taskId ? `${API_BASE_URL}/api/v2/tasks/${taskId}/download/pdf` : ''
+  }, [taskId, API_BASE_URL])
+
+  // Get auth token for PDF preview - memoize to prevent new object reference each render
+  const pdfHttpHeaders = useMemo(() => {
+    const authToken = localStorage.getItem('auth_token_v2')
+    return authToken ? { Authorization: `Bearer ${authToken}` } : undefined
+  }, [])
+
   const handleDownloadPDF = async () => {
     if (!taskId) return
     try {
@@ -101,6 +108,23 @@ export default function ResultsPage() {
     }
   }
 
+  // Show loading while validating task
+  if (isLoading) {
+    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">載入任務結果...</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 (
@@ -127,17 +151,7 @@ export default function ResultsPage() {
     )
   }
 
-  if (isLoading) {
-    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">載入任務結果...</p>
-        </div>
-      </div>
-    )
-  }
-
+  // Fallback for no task detail (shouldn't happen with proper validation)
   if (!taskDetail) {
     return (
       <div className="flex items-center justify-center min-h-[60vh]">
@@ -157,14 +171,6 @@ export default function ResultsPage() {
 
   const isCompleted = taskDetail.status === 'completed'
 
-  // Construct PDF URL for preview
-  const API_BASE_URL = import.meta.env.VITE_API_BASE_URL || 'http://localhost:8000'
-  const pdfUrl = taskId ? `${API_BASE_URL}/api/v2/tasks/${taskId}/download/pdf` : ''
-
-  // Get auth token for PDF preview
-  const authToken = localStorage.getItem('auth_token_v2')
-  const pdfHttpHeaders = authToken ? { Authorization: `Bearer ${authToken}` } : undefined
-
   return (
     <div className="space-y-6">
       {/* Page Header */}