Caching and compressing image proxy

[Zaczero]

Currently, when using markdown, images are served as-is. To enhance performance and user privacy, we should implement a caching and compressing image proxy. This would:

• Reduce page load time
• Decrease bandwidth usage, especially noticeable in user diaries with large image files
• Mask users' IP addresses from external endpoints

As the NextGen platform, we should strive for better higher standards.

The URL rewrite can be implemented in the _render_image method.

The proxy should:

• Limit image size in megapixels to a reasonable value
• Compress files without noticeable loss in quality
• Cache processed images for improved performance

[Zaczero]

I will take care of that issue just before or shortly after the public release. I have done similar work in the past.