Use the correct restart icon for Learn phrase restart

[KSemenenko]

Problem

The Learn RSVP Restart phrase control currently shows the recording target icon, which reads as record/target rather than restarting the current phrase.

Acceptance criteria

• The Restart phrase button uses a restart/replay-style icon instead of the recording target icon.
• The loop control remains visually distinct from the phrase restart control.
• Component coverage asserts the restart button renders the restart glyph and does not render the record target glyph.

Verification expected

• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.Tests/PrompterOne.Web.Tests.csproj

[KSemenenko]

Implemented in local commit de95289.

What changed:

• Added a reusable UiIconKind.Restart glyph with a restart/replay-style circular arrow.
• Updated the Learn Restart phrase button to use the restart glyph instead of RecordTarget.
• Added component coverage proving the restart button renders the restart path and not the record target circle.

Validation:

• dotnet format ./PrompterOne.slnx --include src/PrompterOne.Shared/Components/UiIconKind.cs src/PrompterOne.Shared/Components/UiIcon.razor src/PrompterOne.Shared/Learn/Pages/LearnPage.razor tests/PrompterOne.Web.Tests/AppShell/ScreenShellContractTests.cs
• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.Tests/PrompterOne.Web.Tests.csproj - passed, 629/629
• dotnet test @./tests/dotnet-test-progress.rsp --project ./tests/PrompterOne.Web.UITests.Reader/PrompterOne.Web.UITests.Reader.csproj - passed, 176/176
• dotnet test @./tests/dotnet-test-progress.rsp --solution ./PrompterOne.slnx - passed, 1191/1191
• dotnet publish ./src/PrompterOne.Web/PrompterOne.Web.csproj -c Release -o ./artifacts/publish/PrompterOne.Web - passed

Ready for verification. After the release that includes this commit is cut, add the app version/build number here before closing.