Move GHCR image namespace to the Apollo-Reborn org

The repo moved to Apollo-Reborn/apollo-backend, so the published image
is now ghcr.io/apollo-reborn/apollo-backend. Update the docker-compose
default image and the Getting Started guide reference to match.

Author: nickclyde

GETTING_STARTED.md

@@ -151,7 +151,7 @@ cd apollo-backend
 ```
 
 You **do not need Go or any build tools.** The bundled `docker-compose.yml` pulls a prebuilt image
-from GitHub Container Registry (`ghcr.io/nickclyde/apollo-backend`) automatically.
+from GitHub Container Registry (`ghcr.io/apollo-reborn/apollo-backend`) automatically.
 
 > **Only if you fork and change the code:** you'll need to build your own image instead of pulling.
 > Use `make docker-build` (or `docker compose up -d --build`). Note that `docker compose up` reuses

docker-compose.yml

@@ -8,7 +8,7 @@ x-worker: &worker
   build:
     context: .
     dockerfile: Dockerfile
-  image: ${APOLLO_IMAGE:-ghcr.io/nickclyde/apollo-backend:latest}
+  image: ${APOLLO_IMAGE:-ghcr.io/apollo-reborn/apollo-backend:latest}
   <<: *app-env
   volumes: *app-volumes
   depends_on:
@@ -110,7 +110,7 @@ services:
     build:
       context: .
       dockerfile: Dockerfile
-    image: ${APOLLO_IMAGE:-ghcr.io/nickclyde/apollo-backend:latest}
+    image: ${APOLLO_IMAGE:-ghcr.io/apollo-reborn/apollo-backend:latest}
     command: ["api"]
     <<: *app-env
     volumes: *app-volumes