Fix: Correctly generate thumbnail URLs for path-style and virtual-hosted S3 providers

[lukmay]

This PR resolves an issue where image thumbnails fail to load when using a self-hosted, S3-compatible object storage provider with a public custom domain. The fix updates the thumbnail generation logic to correctly handle both path-style and virtual-hosted (subdomain) style URLs based on environment variables.

The Problem

When self-hosting with an S3-compatible provider that uses a public custom domain (e.g., Cloudflare R2), the /api/thumbnail endpoint was not correctly using the public URL from the CAP_AWS_BUCKET_URL environment variable. Instead, it would fall back to generating pre-signed URLs or incorrect raw URLs, causing the upstream image fetch by the Next.js server to fail with a 404 Not Found error.

This resulted in broken image thumbnails across the dashboard:

The Solution

The /api/thumbnail/route.ts file has been updated to implement more robust URL generation logic:

• The API route now uses the S3_PATH_STYLE environment variable as a switch to determine the correct URL structure.
• If S3_PATH_STYLE is true (for providers like MinIO), it constructs a path-style URL: http://<endpoint>/<bucket>/<key>.
• If S3_PATH_STYLE is false (for providers like Cloudflare R2), it constructs a virtual-hosted style URL using the public CAP_AWS_BUCKET_URL: https://<custom_domain_url>/<key>.
• This ensures the correct public URL is always used when a custom storage configuration is provided, making the application compatible with a wider range of self-hosting setups.

How to Test

1. Configure a self-hosted environment using an S3-compatible provider and a public custom domain.
2. Set the S3_PATH_STYLE and CAP_AWS_BUCKET_URL environment variables according to your provider's requirements.
3. Build the Docker image with this code change.
4. Launch the application and upload a new video.
5. Verify that the video thumbnail loads correctly and that there are no 404 errors related to image fetching.

This change significantly improves the self-hosting experience for a wider range of S3-compatible storage providers. Thank you for considering this contribution.