fix: IPMI access for bee user + remove chart legend

- Add udev rule: /dev/ipmi0 readable by 'ipmi' group (no sudo needed)
- Add 'ipmi' group creation and bee user membership in chroot hook
- Remove legend from all charts (data shown in GPU table below)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/config/hooks/normal/9000-bee-setup.hook.chroot

@@ -15,7 +15,8 @@ ensure_bee_console_user() {
     mkdir -p /home/bee
     chown -R bee:bee /home/bee
     echo "bee:eeb" | chpasswd
-    usermod -aG sudo,video,input,render bee 2>/dev/null || true
+    groupadd -f ipmi 2>/dev/null || true
+    usermod -aG sudo,video,input,render,ipmi bee 2>/dev/null || true
 }
 
 ensure_bee_console_user