Internal Communication Software Development

I need a custom-built software solution whose sole focus is to improve how our internal employees communicate with each other day-to-day. At the moment messages and announcements are scattered across e-mail threads and improvised chat groups, making it hard to keep everyone aligned. I want a single, easy-to-use space—be it web-based, desktop, or mobile—that lets staff chat one-to-one, open topic channels, share files, and receive time-critical broadcasts without noise. Key capabilities I have in mind include real-time messaging, searchable conversation history, role-based access for different departments, and basic admin analytics so I can see engagement levels. You are welcome to suggest the most appropriate tech stack; I am comfortable with mainstream frameworks such as React, Vue, Flutter, .NET, or Laravel as long as the end result is secure, maintainable, and can scale with roughly 300 users within the first year. I’m looking for: • A clickable prototype for early feedback • An MVP that covers core chat, notifications, and user management • Documentation and hand-off so my in-house IT team can maintain it Please outline any similar communication tools you have delivered, the stack you propose, and a ballpark timeline for prototype, MVP, and full release.