Add query param to cache uploads

Add query param `cache` to mark if the content should be cached or not

If query param is present images should be uploaded to cfi and other content to R2

Tasks:

1. In `/pinFile` handler
2. If `cache=true`
3. in mime-type starts with `image` save to cfi
4. else save to R2

Start at the `/pinFile` handler and trace the existing upload paths and MIME-type handling. Implement the stated `cache=true` behavior, then verify that images go to cfi and other content goes to R2; the issue does not name a test or file to run.

Written by the indexing model from the issue text.