Build Personal Schedule Reminder Web App

I want a lightweight, browser-based application that helps me keep my own schedule on track. I am the sole user, so the interface can stay simple-no multi-account management is necessary. The one feature I absolutely need is the ability to set events or tasks and have the system remind me at the right moment, either through in-browser notifications, email, or another reliable method you suggest. The app should open cleanly on any modern desktop or mobile browser, let me add, edit, and delete entries quickly, and store everything in a small database I can back up or export (CSV or JSON is fine). A minimal login to protect my data is welcome, but nothing heavier than it needs to be. Feel free to choose the stack you work fastest with-React + Firebase, Vue + Laravel, Django, plain PHP, or something comparable-as long as you outline how the reminder service will trigger and deliver notifications. Deliverables Responsive single-user web application deployed on my hosting or VPS Working reminder system with accurate, test-verified notifications Source code with a brief setup & usage guide Simple data export/backup option (CSV or JSON) I'll consider the project complete once I can enter a test event, wait for the scheduled time, and reliably receive the alert exactly as specified.