dysconnect is right…
The web app would need to connect to a server that holds the chain. But the user would still have to have the personal wallet. Which for safety would be on their machine.
You’d also need to modify how the program works by enabling multiple wallets and having security on the wallets and not the core…so it becomes more like 2 separate entities.
You can use IndexedDB to store much things for a long time, but again the security and feasibility of using IDB is an issue.