feat(image): add Fal.ai image generation provider support

[erkamkavak]

Summary

Added Fal.ai as an image generation provider alongside OpenAI. Implemented proxy API endpoint for Fal.ai with streaming status support, queue-based generation, and execution file storage. Updated image generator block to support provider selection with conditional model and parameter fields for both OpenAI (DALL-E 3, GPT Image) and Fal.ai models.

Type of Change

• [ ] Bug fix
• [x] New feature
• [ ] Breaking change
• [ ] Documentation
• [ ] Other: ___________

Testing

How has this been tested? What should reviewers focus on?

Checklist

• [x] Code follows project style guidelines
• [x] Self-reviewed my changes
• [ ] Tests added/updated and passing
• [x] No new warnings introduced
• [x] I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

Screenshots/Videos

I haven't tested it yet throughly. Also I believe openai image can be moved from openai folder to image folder and all image generation providers can implemented there.

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