docs: document terraform import for incus containers and remove korax

Add comprehensive terraform import documentation for Incus resources.
Includes syntax for importing containers with for_each keys, retrieving
image fingerprints, and specific import commands for Uranian hosts.
Covers troubleshooting for common import issues and state verification.
Removes obsolete korax.helu.ca host from ansible inventory.

ansible/inventory/host_vars/korax.helu.ca.yml

@@ -1,20 +0,0 @@
----
-# Korax Configuration
-# Services: alloy, kernos
-
-services:
-  - alloy
-  - kernos
-
-# Alloy
-alloy_log_level: "warn"
-# Kernos MCP Shell Server Configuration
-kernos_user: harper
-kernos_group: harper
-kernos_directory: /srv/kernos
-kernos_port: 22021
-kernos_host: "0.0.0.0"
-kernos_log_level: INFO
-kernos_log_format: json
-kernos_environment: sandbox
-kernos_allow_commands: "apt,awk,base64,bash,cat,chmod,cp,curl,cut,date,dd,df,dig,dmesg,du,echo,env,file,find,free,git,grep,gunzip,gzip,head,host,hostname,id,jq,kill,less,ln,ls,lsblk,lspci,lsusb,make,mkdir,mv,nc,node,nohup,npm,npx,ping,pip,pkill,pnpm,printenv,ps,pwd,python3,rm,rsync,run-captured,scp,sed,sleep,sort,source,ssh,ssh-keygen,ssh-keyscan,stat,sudo,tail,tar,tee,timeout,touch,tr,tree,uname,uniq,unzip,uptime,wc,wget,which,whoami,xargs,xz,zip"

ansible/inventory/host_vars/portia.incus.yml

@@ -3,7 +3,6 @@
 # Services: alloy, postgresql
 # Note: PgAdmin moved to Prospero (PPLG stack)
 
-ansible_user: robert
 
 services:
   - alloy

ansible/inventory/host_vars/prospero.incus.yml

@@ -2,7 +2,6 @@
 # Prospero Configuration - PPLG Observability & Admin Stack
 # Services: pplg (PgAdmin, Prometheus, Loki, Grafana + OAuth2-Proxy)
 
-ansible_user: robert
 
 services:
   - alloy

ansible/inventory/host_vars/puck.incus.yml

@@ -2,8 +2,6 @@
 # Puck Configuration - Application Runtime
 # Services: alloy, docker, lxqt, jupyterlab
 
-ansible_user: robert
-
 services:
   - alloy
   - docker

ansible/inventory/host_vars/rosalind.incus.yml

@@ -2,8 +2,6 @@
 # Rosalind Configuration - GO, Node.js, PHP Apps
 # Services: alloy, gitea, lobechat, nextcloud
 
-ansible_user: robert
-
 services:
   - alloy
   - anythingllm