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.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

deploy/README.md

@@ -180,9 +180,6 @@ and `web-player/Dockerfile`.
   the comments in `.env.example`).
 - **Zitadel** runs `start-from-init`, which is idempotent: the same command
   works on an empty volume and on an existing one.
-- **`AppSettings*.json` are PascalCase** in `Musify.Api` and `Musify.Worker`;
-  on case-sensitive Linux the host looks for `appsettings*.json`, so their
-  Dockerfiles create lowercase copies at publish time.
 - **Re-running `zitadel-init`, `seaweedfs-init` or `migrate`** is safe: they
   reuse the existing project/apps/bucket by name, and `migrate` is a normal
   `dotnet ef database update`, a no-op once the schema is current.

deploy/compose.yml

@@ -19,7 +19,7 @@
 # file, so the apps start with real values. See deploy/README.md.
 
 # Backend settings that are identical for the API and the Worker. ASP.NET Core
-# maps `__` to `:`, so these override the matching AppSettings.json sections.
+# maps `__` to `:`, so these override the matching appsettings.json sections.
 # POSTGRES_HOST / RABBITMQ_HOST / JAEGER_HOST differ between environments
 # (host.docker.internal in dev, the container name over infra-net in prod,
 # see .env.example / .env.prod.example), same as PUBLIC_AUTH_URL/S3_PUBLIC_URL