CORRECTED FIX: Properly handle SYS_USER_HOME_BASE initialization

Previous attempt (commit 9b0a145) moved ALL variable exports inside the
conditional, which broke the script because variables weren't initialized
on subsequent runs after SYS_DETECTION_COMPLETE was set.

The CORRECT Fix:
Move SYS_USER_HOME_BASE and other session variables INSIDE the conditional
so they're only initialized ONCE, not reset every time system-detect.sh
is sourced.

Changes:
1. lib/system-detect.sh (lines 26-32):
   - Moved SYS_USER_HOME_BASE="" inside conditional
   - Moved SYS_PHP_VERSIONS=() inside conditional
   - Moved firewall variables inside conditional
   - Now all exports only run when SYS_DETECTION_COMPLETE is empty

2. launcher.sh (line 22):
   - Re-added: source "$LIB_DIR/domain-discovery.sh"
   - Lost when reverting broken commit

Impact:
- Fixes Plesk: SYS_USER_HOME_BASE="/var/www/vhosts" persists
- Fixes cPanel: launcher completes successfully and shows menu
- list_all_domains() and all unified functions now available

Tested on cPanel: ✅ WORKING
Ready for Plesk testing

launcher.sh

@@ -19,6 +19,7 @@ CONFIG_DIR="$BASE_DIR/config"
 # Load core libraries
 source "$LIB_DIR/common-functions.sh"
 source "$LIB_DIR/system-detect.sh"
+source "$LIB_DIR/domain-discovery.sh"
 source "$LIB_DIR/user-manager.sh"
 source "$LIB_DIR/reference-db.sh"
 

lib/system-detect.sh

@@ -23,13 +23,13 @@ if [ -z "$SYS_DETECTION_COMPLETE" ]; then
     export SYS_DB_TYPE=""
     export SYS_DB_VERSION=""
     export SYS_LOG_DIR=""
-fi
     export SYS_USER_HOME_BASE=""
     export SYS_PHP_VERSIONS=()
     export SYS_CLOUDFLARE_ACTIVE=""
     export SYS_FIREWALL=""
     export SYS_FIREWALL_VERSION=""
     export SYS_FIREWALL_ACTIVE=""
+fi
 
 #############################################################################
 # CONTROL PANEL DETECTION