Update documentation for S3 protocol on Infomaniaks storage services

[kallioli]

This update enhances the documentation for Infomaniak object storage by:

Adding a new section for S3 access on Infomaniak Public Cloud

    Includes Cyberduck connection profiles for Region dc3-a and dc4-a

    Documents how to generate EC2-compatible credentials via the OpenStack CLI

    Provides troubleshooting tips for AWS Signature V4 errors

Clarifying that Swiss Backup also supports S3

    Credentials are provisioned from the Infomaniak Manager during setup

    Distinction made between Swiss Backup and Public Cloud workflows

Let me know if you'd like me to add screenshots or examples for the Manager-based S3 setup.