Contact person: Fix Flutter In-App Upgrade Flow

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Location: Stockholm, Sweden

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"I’m building a cross-platform Flutter app in VS Code on my Mac and I’ve hit a snag with the free-trial-to-paid upgrade flow. The secure upgrade flag is stored with Keychain/Keystore, and on each launch the app simply reads that local value to decide what to show. Right now, though, tapping “Upgrade Now” in any of the trial reminder or trial-expired dialogs does nothing—no “Upgrade Successful” pop-up, no flag written, and the Upgrade button keeps reappearing.

Debug prints reveal that `[login to view URL]` is coming back null inside `UpgradeScreen`, so the actual upgrade logic never fires. I need someone to trace why that key isn’t initialised, repair the callback chain, and make sure the UI updates correctly afterwards.

Deliverables
• “Upgrade Successful” dialog appears immediately after a valid purchase.
• Upgraded state is written to secure storage and persists across relaunches.
• After successful upgrade, Main menu hides the Upgrade button and refreshes automatically.
• After confirming successful upgrade in dialog, the user is routed back to the main menu, not left on the upgrade screen.
• Clean, commented code change (Git pull request preferred) and a brief note explaining what was fixed so I can learn from it.

Feel free to refactor lightly if it clarifies state management, but keep the existing Keychain/Keystore approach. I can provide the relevant files from the project to be able to make the necessary changes." (client-provided description)