Enhance HTML & Build App

I already have a single-page HTML file that works well as a static mock-up, but I now need it to do much more. The job starts with adding real functionality:

• New sections: a secure user-login area, a clean contact form that sends mail or stores submissions, and interactive elements (think modals, accordions, or sliders) that make the page feel like a true application. I also want a simple backup-data routine so the user’s basic settings or form submissions are saved locally or in the cloud.

Once those pieces are in place, I’d like the upgraded page converted into an installable app. I’m open to the technology you prefer—Cordova, Capacitor, React Native, Flutter WebView, or a similar solution—as long as the final build installs smoothly on both Android and iOS and mirrors the new functionality.

Deliverables
1. Updated HTML/CSS/JS source with the new sections fully wired.
2. Source code for the chosen app wrapper.
3. Signed APK and iOS build (TestFlight or .ipa) ready for testing.
4. Brief setup notes so I can reproduce the build myself.

Acceptance criteria
• Login authenticates and handles basic password reset.
• Contact form successfully delivers or stores messages.
• Interactive elements respond without errors on mobile and desktop.
• App versions pass store pre-flight checks (no security or performance flags).

If something in my outline needs clarification, let me know—I’m happy to refine the scope so you can quote accurately and hit the ground running.