feat: enhance layout preprocessing and unify image scaling proposal

Backend changes:
- Add image scaling configuration for PP-Structure processing
- Enhance layout preprocessing service with scaling support
- Update OCR service with improved memory management
- Add PP-Structure enhanced processing improvements

Frontend changes:
- Update preprocessing settings UI
- Fix processing page layout and state management
- Update API types for new parameters

Proposals:
- Archive add-layout-preprocessing proposal (completed)
- Add unify-image-scaling proposal for consistent coordinate handling

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

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

frontend/src/services/apiV2.ts

@@ -408,7 +408,7 @@ class ApiClientV2 {
    * Analyze document to get recommended processing track
    */
   async analyzeDocument(taskId: string): Promise<DocumentAnalysisResponse> {
-    const response = await this.client.get<DocumentAnalysisResponse>(`/tasks/${taskId}/analyze`)
+    const response = await this.client.post<DocumentAnalysisResponse>(`/tasks/${taskId}/analyze`)
     return response.data
   }