frontend: bypass auth middleware for favicon and icon assets in root

[jecr]

Updated the ServeHTTP function in the assetHandler to add caching headers for .ico, .svg, and .webp files, serving these files with a Cache-Control header set to cache for one day.

This change bypasses the authentication middleware for favicon and icon assets in the root directory. The bypass is limited to image assets in the root path to maintain security.

Key changes:

• Added early path check for image file extensions (.ico, .svg, .webp)
• Added security check to only serve files from root directory
• Set Cache-Control header to cache assets for 24 hours
• Serve files directly without going through auth middleware