refactor: update paths and structure for server services in Docker and documentation (#7333)

- Changed references from 'apiserver' to 'apps/server' in Docker configurations and environment setup.
- Updated contributing documentation to reflect the new service structure.
- Adjusted setup script to accommodate the new directory layout.
- Removed obsolete files related to the previous structure.

deploy/selfhost/build.yml

@@ -20,7 +20,7 @@ services:
   api:
     image: ${DOCKERHUB_USER:-local}/plane-backend:${APP_RELEASE:-latest}
     build:
-      context: ./apiserver
+      context: ./apps/server
       dockerfile: ./Dockerfile.api
 
   proxy: