Secure Remote Support Tool Development

I need a full-featured remote support application that mirrors the core experience of LogMeIn Rescue or TeamViewer but is completely custom to my organization. The end goal is a pair of lightweight apps—one for customers and one for technicians—that connect through a unique session code, give technicians real-time desktop control, and maintain rock-solid security.

Scope of work
• Build customer and technician executables for Windows and Mac.
• Implement username-and-password authentication, with all traffic fully encrypted.
• Provide fast, stable remote-desktop viewing/control, file transfer, and live chat.
• Allow drag-to-generate session codes so a technician can join quickly, juggling multiple sessions from one console.
• Design a simple, modern UI so non-technical end users can launch support in seconds.
• Engineer the back-end infrastructure to remain scalable as usage grows.

Acceptance criteria
1. Technician can connect to any supported OS within five seconds of code entry.
2. Input, screen, file, and chat data stay encrypted in transit.
3. A single technician console handles at least five concurrent customer sessions without lag.
4. Installers are under 25 MB and require no admin rights on launch for end users.
5. Source code and build instructions are delivered, along with clear deployment documentation.

When you respond, please include examples of past remote-desktop or RDP-related work, the tech stack you propose, a timeline broken into milestones, and a realistic cost estimate for completing the above deliverables.