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>

openspec/changes/archive/2025-12-11-simple-text-positioning/design.md

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+# Design: Simple Text Positioning
+
+## Architecture
+
+### Current Flow (Complex)
+```
+Raw OCR → PP-Structure Analysis → Table Detection → HTML Parsing →
+Column Correction → Cell Positioning → PDF Generation
+```
+
+### New Flow (Simple)
+```
+Raw OCR → Text Region Extraction → Bbox Processing →
+Rotation Calculation → Font Size Estimation → PDF Text Rendering
+```
+
+## Core Components
+
+### 1. TextRegionRenderer
+
+New service class to handle raw OCR text rendering:
+
+```python
+class TextRegionRenderer:
+    """Render raw OCR text regions to PDF."""
+
+    def render_text_region(
+        self,
+        canvas: Canvas,
+        region: Dict,
+        scale_factor: float
+    ) -> None:
+        """
+        Render a single OCR text region.
+
+        Args:
+            canvas: ReportLab canvas
+            region: Raw OCR region with text and bbox
+            scale_factor: Coordinate scaling factor
+        """
+```
+
+### 2. Bbox Processing
+
+Raw OCR bbox format (quadrilateral - 4 corner points):
+```json
+{
+  "text": "LOCTITE",
+  "bbox": [[116, 76], [378, 76], [378, 128], [116, 128]],
+  "confidence": 0.98
+}
+```
+
+Processing steps:
+1. **Center point**: Average of 4 corners
+2. **Width/Height**: Distance between corners
+3. **Rotation angle**: Angle of top edge from horizontal
+4. **Font size**: Approximate from bbox height
+
+### 3. Rotation Calculation
+
+```python
+def calculate_rotation(bbox: List[List[float]]) -> float:
+    """
+    Calculate text rotation from bbox quadrilateral.
+
+    Returns angle in degrees (counter-clockwise from horizontal).
+    """
+    # Top-left to top-right vector
+    dx = bbox[1][0] - bbox[0][0]
+    dy = bbox[1][1] - bbox[0][1]
+
+    # Angle in degrees
+    angle = math.atan2(dy, dx) * 180 / math.pi
+    return angle
+```
+
+### 4. Font Size Estimation
+
+```python
+def estimate_font_size(bbox: List[List[float]], text: str) -> float:
+    """
+    Estimate font size from bbox dimensions.
+
+    Uses bbox height as primary indicator, adjusted for aspect ratio.
+    """
+    # Calculate bbox height (average of left and right edges)
+    left_height = math.dist(bbox[0], bbox[3])
+    right_height = math.dist(bbox[1], bbox[2])
+    avg_height = (left_height + right_height) / 2
+
+    # Font size is approximately 70-80% of bbox height
+    return avg_height * 0.75
+```
+
+## Integration Points
+
+### PDFGeneratorService
+
+Modify `draw_ocr_content()` to use simple text positioning:
+
+```python
+def draw_ocr_content(self, canvas, content_data, page_info):
+    """Draw OCR content using simple text positioning."""
+
+    # Use raw OCR regions directly
+    raw_regions = content_data.get('raw_ocr_regions', [])
+
+    for region in raw_regions:
+        self.text_renderer.render_text_region(
+            canvas, region, scale_factor
+        )
+```
+
+### Configuration
+
+Add config option to enable/disable simple mode:
+
+```python
+class OCRSettings:
+    simple_text_positioning: bool = Field(
+        default=True,
+        description="Use simple text positioning instead of table reconstruction"
+    )
+```
+
+## File Changes
+
+| File | Change |
+|------|--------|
+| `app/services/text_region_renderer.py` | New - Text rendering logic |
+| `app/services/pdf_generator_service.py` | Modify - Integration |
+| `app/core/config.py` | Add - Configuration option |
+
+## Edge Cases
+
+1. **Overlapping text**: Regions may overlap slightly - render in reading order
+2. **Very small text**: Minimum font size threshold (6pt)
+3. **Rotated pages**: Handle 90/180/270 degree page rotation
+4. **Empty regions**: Skip regions with empty text
+5. **Unicode text**: Ensure font supports CJK characters