feat: enable document orientation detection for scanned PDFs

- Enable PP-StructureV3's use_doc_orientation_classify feature
- Detect rotation angle from doc_preprocessor_res.angle
- Swap page dimensions (width <-> height) for 90°/270° rotations
- Output PDF now correctly displays landscape-scanned content

Also includes:
- Archive completed openspec proposals
- Add simplify-frontend-ocr-config proposal (pending)
- Code cleanup and frontend simplification

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/pages/TaskDetailPage.tsx

@@ -1,7 +1,7 @@
 import { useMemo, useState, useEffect } from 'react'
 import { useParams, useNavigate } from 'react-router-dom'
 import { useTranslation } from 'react-i18next'
-import { useQuery, useQueryClient } from '@tanstack/react-query'
+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'
@@ -62,7 +62,6 @@ export default function TaskDetailPage() {
   const { t } = useTranslation()
   const navigate = useNavigate()
   const { toast } = useToast()
-  const queryClient = useQueryClient()
 
   // TaskStore for caching
   const { updateTaskCache } = useTaskStore()