feat(cloudpex): site values out of the script, prompted at install into /etc/cloudpex.conf

cloudpex/cloudpex no longer carries the NAS host, share name, SMB user,
mount point or SMB version. It reads /etc/cloudpex.conf (root:root 0600,
KEY=value) line by line, never sources it, and dies with a hint when the
file is missing, incomplete or has a relative mount point.

cloudpex/install.sh prompts for the five values (regex-validated, re-asked
on bad input so the main installer never aborts), shows and keeps an
existing config unless answered n, and skips the config when no terminal
is attached. README (FR) + root README + CLAUDE.md updated.

CLAUDE.md

@@ -26,7 +26,8 @@ etc/profile.d/disk-usage-warning.sh     login-time low-disk warning → /etc/pro
 etc/tmpfiles.d/tmp.conf                 disk-backed /tmp cleanup rules (offer: /tmp on disk)
 etc/systemd/ssh.service.d/override.conf sshd OOM-exempt drop-in (offer: SSH memory guard)
 etc/default/earlyoom                    earlyoom args, spare sshd / kill node first (same offer)
-cloudpex/{cloudpex,install.sh,README.md} on-demand CloudPex SMB mount helper → /usr/local/bin (FR docs)
+cloudpex/{cloudpex,install.sh,README.md} on-demand SMB mount helper → /usr/local/bin; site values
+                                         prompted at install → /etc/cloudpex.conf, never in the script (FR docs)
 .claude/{tasks,memory,audits}/   Claude working state
 ```