Flutter Developer Needed to Upgrade Existing WebView Browser App (Proxy & Firebase Integration)

I already have a working Flutter-based WebView browser app. This is NOT a new app development.
I need an experienced Flutter developer to upgrade and extend the existing application.

Update Scope:
- The browser already opens websites via Google Search by default.
- If a website fails to load due to:
HTTP errors (403, 401, 451),
Network errors (ERR_CONNECTION_RESET, ERR_CONNECTION_REFUSED, ERR_ADDRESS_UNREACHABLE),
SSL errors (ERR_SSL_PROTOCOL_ERROR, Handshake Failure),
DNS errors (ERR_NAME_NOT_RESOLVED),
the app should automatically retry loading the website using a proxy.

- The app is already connected to Firebase with an admin panel.
- Proxy settings (domain, username, password) must be managed from the Firebase admin panel.
- Any change made in the admin panel should reflect instantly in the browser app.
- The proxy must work reliably with the existing WebView setup.

Requirements:
- Strong experience with Flutter and WebView
- Proxy and network handling knowledge
- Firebase integration experience
- Ability to work with an existing codebase

This is an update and system integration task for an existing browser app.
Only experienced Flutter developers should apply.