Build me a private website where users can upload and collaboratively annotate photos/videos

Industry: Creative/Media Type of website: Private/Internal Intranet BUSINESS PROBLEM: In my creative design company, we are trying to give each other feedback over e-mail which is not that secure and is hard to collate multiple bits of feedback. We would like to create a platform which is both secure and tracks changes/feedback. WHAT I NEED: I need to create a intranet/website which allows users to upload photos and videos. Selected users on the platform should then be allowed to give feedback on pictures and video in the form of annotations. This could be overlaying text or shapes, so the original uploader can make changes accordingly. There should also should be an option to accept the picture/video if all is OK and no changes need to be made. These actions should notify users by email. The original uploader should be able to select (by individuals or by groups) who has access and who should review each photo and video. This could be a number of people reviewing before a approve notification is created, and should have the ability to become hierarchical (ie Junior Designer approves first, followed by Head of Design followed by Director). This should be a secure platform, so designers only have access to their workstreams defined by groups/individual permissions. I expect 50-100 to be using this website to start off with, but there needs to be room to add features and grow the number of users. If you have any questions, please don't hesitate to contact me. Thanks Jack