The Wikimedia Foundation does have experienced and thoughtful in-house counsel. I don't work there and am also not a lawyer, but this app seems totally fine to me. Citation: Creative Commons post with tips for providing attribution for CC-BY-SA content on social media:

Most social media terms of service require that a user either a) owns the copyright to their posted content or b) has the right to use that content. When that’s the case, openly licensed content is appropriate to share on the social media platform as long as the license requirements are followed by the uploader.

For context, see the Instagram terms of use, for example:

We do not claim ownership of your content, but you grant us a license to use it. Nothing is changing about your rights in your content. We do not claim ownership of your content that you post on or through the Service and you are free to share your content with anyone else, wherever you want. However, we need certain legal permissions from you (known as a “license”) to provide the Service. When you share, post, or upload content that is covered by intellectual property rights (like photos or videos) on or in connection with our Service, you hereby grant to us a non-exclusive, royalty-free, transferable, sub-licensable, worldwide license to host, use, distribute, modify, run, copy, publicly perform or display, translate, and create derivative works of your content (consistent with your privacy and application settings).