Switch container registry to Gitea built-in (gitea.dcglab.co.uk/steve/kb)

The standalone Registry v2 host (docker.dcglab.co.uk, briefly registry.dcglab.co.uk)
is being scrapped. Move all kb images to Gitea's built-in container registry.

README.md

@@ -33,7 +33,7 @@ docker run -d --name kb-engine \
   -e KB_DEVICE=auto \
   -e KB_API_KEY=your-secret-key \
   --restart unless-stopped \
-  docker.dcglab.co.uk/dcg/kb/engine:latest-nvidia
+  gitea.dcglab.co.uk/steve/kb/engine:latest-nvidia
 
 # CPU only (no GPU required — smaller image)
 docker run -d --name kb-engine \
@@ -42,7 +42,7 @@ docker run -d --name kb-engine \
   -e KB_MODEL=all-MiniLM-L6-v2 \
   -e KB_API_KEY=your-secret-key \
   --restart unless-stopped \
-  docker.dcglab.co.uk/dcg/kb/engine:latest-cpu
+  gitea.dcglab.co.uk/steve/kb/engine:latest-cpu
 ```
 
 Or use a compose file from the repo: