Fix Trip Editor public progress URL

[stef-k]

Summary

Fixes #308.

Root cause: Trip Editor metadata URL generation used Url.Action("View", "TripViewer", new { area = "Public", ... }). Because the public trip view endpoint is an attribute route, MVC could fall back to the conventional public-area route and generate /Public/TripViewer/View/{tripId} instead of the canonical /Public/Trips/{tripId} route.

Before:

• public URL could generate https://example.test/Public/TripViewer/View/{tripId}
• progress URL generated https://example.test/Public/TripViewer/View/{tripId}?progress=1

After:

• public URL generates https://example.test/Public/Trips/{tripId}
• progress URL generates https://example.test/Public/Trips/{tripId}?progress=1

Implementation notes:

• Named the existing public trip view attribute route as PublicTripView.
• Updated Trip Editor read-state/metadata generation to use Url.RouteUrl(...) against that named route.
• Strengthened controller tests so the previous Url.Action(...) path is no longer masked by a permissive URL-helper mock.

Validation

• dotnet test tests/Wayfarer.Tests/Wayfarer.Tests.csproj --filter "FullyQualifiedName~TripEditorControllerTests|FullyQualifiedName~TripEditorTagsShareProgressControllerTests|FullyQualifiedName~TripEditorMetadataControllerTests" - passed, 46 tests
• dotnet build - passed, 0 warnings/errors
• dotnet test - passed, 1548 tests
• dotnet run --project tools/Wayfarer.LocCheck -- --warn 400 --fail 600 - passed with existing warning-threshold files; no hard failures
• git diff --check origin/main...HEAD - passed
• git ls-files -- .local playwright-report test-results screenshots traces wwwroot/vite/trip-editor wwwroot/dist - no tracked artifacts reported

Manual deployed validation is still required after this PR is deployed, because the fix has been validated locally through backend route-generation tests and not against the deployed environment that originally produced the 404.