Clean up backend and web-player leftovers

Remove dead scaffold/config cruft and stale references left over from
recent refactors: dotnet's WebApi.http template file, the AppSettings
PascalCase/Dockerfile workaround (renamed to appsettings.json to match
convention), empty directories left behind by the auth-route and
folder-structure moves, a stale ESLint ignore, and the now-fully-applied
frontend refactor plan doc.

.gitignore

@@ -7,6 +7,9 @@ obj/
 *.userosscache
 .vs/
 artifacts/
+TestResults/
+*.trx
+*.coverage
 
 # Rider / VS
 .idea/