I already have a desktop billing program running smoothly in-house and now want the same functionality available through any modern browser. I will share the full source code, database schema and a feature list once we start, but in essence the scope is: • Move every current feature to a web-based application that can be accessed over HTTPS. • Build a simple, secure user-authentication layer (email + password is fine for now; role management is a plus). • Apply a handful of small tweaks that I will outline—mostly UI polish and a couple of extra filters in the reports. I need an estimate of both cost and turnaround time for the complete migration, including deployment on my hosting account and basic post-launch support. Please factor in code hand-off documentation so I can maintain the system later. Feel free to suggest the stack you are most comfortable with; I am open as long as it is reliable and easy to maintain.