feat: Improve image generation prompts with visual data extraction

- Add dedicated image_generation module with statistical extraction
- Support 16 industry domains with visual concept detection
- Add model-specific guidance for Ideogram, FLUX, GLM, Qwen, MAI
- Extract statistics, rankings, comparisons, and trends automatically
- Refactor backend/api/images.py to use new module

frontend/src/components/ImageGen/ImageGenerator.tsx

@@ -9,7 +9,7 @@ import InfoIcon from '@mui/icons-material/Info';
 import { useImageGeneration, ImageGenerationRequest, fetchPromptSuggestions } from './useImageGeneration';
 
 type Provider = 'huggingface' | 'stability' | 'wavespeed';
-type ImageType = 'realistic' | 'chart' | 'conceptual' | 'diagram' | 'illustration' | 'background';
+type ImageType = 'realistic' | 'chart' | 'conceptual' | 'diagram' | 'illustration' | 'background' | 'infographic';
 
 interface ImageGeneratorProps {
   defaultProvider?: Provider;