Improve docker files and use a non-root user

docker/variables.sh

@@ -4,7 +4,6 @@ declare -A ALLTALK_VARS
 ALLTALK_VARS["CUDA_VERSION"]=12.6.0
 ALLTALK_VARS["PYTHON_VERSION"]=3.11.11
 ALLTALK_VARS["DEEPSPEED_VERSION"]=0.16.2
-ALLTALK_VARS["ALLTALK_DIR"]=/opt/alltalk
 
 # Export single variables (needed by Docker locally)
 for key in "${!ALLTALK_VARS[@]}"