File Upload API

Available endpoints:

• POST /upload/logo - Upload logo (max 2MB, images only)
• POST /upload/cover - Upload cover image (max 5MB, images only)
• POST /upload/general - Upload any file (max 50MB)
• POST /upload/gpx - Upload GPX file (max 200MB)
• GET /images/:type - View all images of a type (logos, covers, general)
• GET /images/:type/:filename - View specific image

Use form-data with field name "image" for images, "file" for general/GPX files