Describe the bug

When web makes requests to the previews webdav endpoint, a 429 Too Many Requests error can occur, possibly with a Retry-After header. Web doesn't react with retries at the moment.

Steps to reproduce

1. Limit the thumbnail service to 2 concurrent preview image creations via THUMBNAILS_MAX_CONCURRENT_REQUESTS env var
2. Request 10 images via file list

Expected behavior

The failed requests don't get retried.

Actual behavior

The web ui should react to 429 responses with retries.

Additional context

There are several places in the code / ui where preview requests happen and can fail:

• files list
• tiles view
• right sidebar "Details" panel
• preview app (especially in the pre-fetching of images)

All of those requests should be retried if they failed with a 429 status code. If the response has a Retry-After header it should be respected. If it's absent we should come up with a suitable retry offset on our own.

Backend context:

• move thumbnailer ratelimiter to grpc service ocis#10225
• fix(webdav): Set Retry-After header for 429 responses ocis#10280