refactor(cleanup): retire the dead SFTP 'Docker Manager User' to unused/

CFG_DOCKER_MANAGER_USER / installDockerManagerUser was a chrooted SFTP file-access
user — unrelated to the LibrePortal control-plane manager (sudo_user_name), and
the source of the 'two managers' confusion. It was permanently-off dead code: the
gate CFG_DOCKER_MANAGER_ENABLED and the CFG_DOCKER_MANAGER_USER/_PASS keys are
defined in no config template, so it never ran. Its SSH-key-management sibling
(unused/ssh_manager.sh) was already retired; admin host SSH access is handled by
the current /ssh page + scripts/ssh/host_access.sh.

Move install_user_manager.sh / uninstall_user_manager.sh / check_manager.sh to
scripts/unused/manager/ (recoverable, matches the graveyard convention — not
deleted, in case the SFTP-user idea is rebuilt cleanly later), drop the two call
sites (start_preinstall.sh, check_requirements.sh), regenerate the arrays.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>

scripts/checks/check_requirements.sh

@@ -19,7 +19,6 @@ checkRequirements()
 	checkDockerNetworkRequirement;
 	checkUFWRequirement;
 	checkUFWDRequirement;
-	checkManagerRequirement;
 	checkSSLCertsRequirement;
 	checkSwapfileRequirement;
 	checkCrontabRequirement;

scripts/source/files/arrays/files_checks.sh

@@ -18,7 +18,6 @@ checks_scripts=(
     "checks/requirements/check_docker.sh"
     "checks/requirements/check_docker_switcher.sh"
     "checks/requirements/check_install_type.sh"
-    "checks/requirements/check_manager.sh"
     "checks/requirements/check_passwords.sh"
     "checks/requirements/check_root.sh"
     "checks/requirements/check_sslcerts.sh"

scripts/source/files/arrays/files_install.sh

@@ -11,7 +11,5 @@ install_scripts=(
     "install/install_swapfile.sh"
     "install/install_ufwd.sh"
     "install/install_ufw.sh"
-    "install/manager/install_user_manager.sh"
-    "install/manager/uninstall_user_manager.sh"
 
 )

scripts/start/start_preinstall.sh

@@ -29,7 +29,6 @@ startPreInstall()
 
     # Both
     installDockerNetwork;
-    installDockerManagerUser
 
     #######################################################
     ###                Install UFW Firewall             ###