# Change: Reflow Layout PDF Export for All Tracks

## Why

When generating translated PDFs, text often doesn't fit within original bounding boxes due to language expansion/contraction differences. Additionally, users may want a readable flowing document format even without translation.

**Example from task c79df0ad-f9a6-4c04-8139-13eaef25fa83:**
- Original Chinese: "华天科技（宝鸡）有限公司设备版块报价单" (19 characters)
- Translated English: "Huatian Technology (Baoji) Co., Ltd. Equipment Division Quotation" (65+ characters)
- Same bounding box: 703×111 pixels
- Current result: Font reduced to minimum (3pt), text unreadable

## What Changes

- **NEW**: Add reflow layout PDF generation for both OCR and Direct tracks
- Preserve semantic structure (headings, tables, lists) in reflow mode
- Use consistent, readable font sizes (12pt body, 16pt headings)
- Embed images inline within flowing content
- **IMPORTANT**: Original layout preservation PDF generation remains unchanged
- Support both tracks with proper reading order:
  - **OCR track**: Use existing `reading_order` array from PP-StructureV3
  - **Direct track**: Use PyMuPDF's implicit order (with option for column detection)
- **FIX**: Remove outdated MADLAD-400 references from frontend (now uses Dify cloud translation)

## Download Options

| Scenario | Layout PDF | Reflow PDF |
|----------|------------|------------|
| **Without Translation** | Available | Available (NEW) |
| **With Translation** | - | Available (single option, unchanged) |

## Impact

- Affected specs: `specs/result-export/spec.md`
- Affected code:
  - `backend/app/services/pdf_generator_service.py` - add reflow generation method
  - `backend/app/routers/tasks.py` - add reflow PDF download endpoint
  - `backend/app/routers/translate.py` - use reflow mode for translated PDFs
  - `frontend/src/pages/TaskDetailPage.tsx`:
    - Add "Download Reflow PDF" button for original documents
    - Remove MADLAD-400 badge and outdated description text
