Setup/docs issues on Windows (ports, callbacks, scopes, and DB init)

[Youdaman]

I got this sample running on Windows, but hit a few setup issues that might help others:

• Default ports 5000/5001 can conflict on Windows (often due to Hyper-V/Docker). Consider using alternatives like 3000/3001 (or any free pair).
• In Construct the Database, migration commands are wrapped in HTML tags instead of Markdown code blocks, so they're easy to miss.
• The README doesn't clearly call out adding all required callback URLs in the Xero app config. Missing these causes Invalid redirect_uri during OAuth.
• Default scopes are quite broad for local dev and can trigger Invalid scope for client during OAuth if the app doesn't have all scopes enabled.
• It may help to include an optional dotnet restore before dotnet build (especially after git clean -xdf).

Suggested command sequence:

dotnet restore
dotnet ef migrations add InitialCreate
dotnet ef database update
dotnet build
dotnet run