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-use-cellboxes-for-table-rendering/specs/document-processing/spec.md

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+# document-processing Specification Delta
+
+## MODIFIED Requirements
+
+### Requirement: Extract table structure (Modified)
+
+The system SHALL use cell_boxes coordinates as the primary source for table structure when rendering PDFs, with HTML parsing as fallback.
+
+#### Scenario: Render table using cell_boxes grid
+- **WHEN** rendering a table element to PDF
+- **AND** the table has valid cell_boxes coordinates
+- **AND** `table_rendering_prefer_cellboxes` is enabled
+- **THEN** the system SHALL infer row/column grid from cell_boxes coordinates
+- **AND** extract text content from HTML in reading order
+- **AND** map content to grid cells by position
+- **AND** render table borders using cell_boxes coordinates
+- **AND** place text content within calculated cell boundaries
+
+#### Scenario: Handle cell_boxes grid mismatch gracefully
+- **WHEN** cell_boxes grid has different dimensions than HTML colspan/rowspan structure
+- **THEN** the system SHALL use cell_boxes grid as authoritative structure
+- **AND** map available HTML content to cells row-by-row
+- **AND** leave unmapped cells empty
+- **AND** log warning if content count differs significantly
+
+#### Scenario: Fallback to HTML-based rendering
+- **WHEN** cell_boxes is empty or None
+- **OR** `table_rendering_prefer_cellboxes` is disabled
+- **OR** cell_boxes grid inference fails
+- **THEN** the system SHALL fall back to existing HTML-based table rendering
+- **AND** use ReportLab Table with parsed HTML structure
+
+#### Scenario: Maintain backward compatibility
+- **WHEN** processing tables where cell_boxes grid matches HTML structure
+- **THEN** the system SHALL produce identical output to previous behavior
+- **AND** pass all existing table rendering tests