refactor(ui): replace neon palette and ad-hoc echo with minimal design system

- reduce color palette to red/cyan/white/gray; alias legacy vars onto CYAN
- add show_box_top/mid/bottom, show_separator, show_menu_item, show_prompt helpers to lib/common.sh
- update apps/index.sh and tools/index.sh to use new UI helpers instead of inline echo/ANSI
- drop BLINK, REV escape codes and remove hardcoded prompt strings from callers

apps/index.sh

@@ -34,7 +34,7 @@ run_sibling() {
 
     local temp_file exit_code
     temp_file=$(mktemp "/tmp/lxs.${script_name%.*}.XXXXXX.sh")
-    echo -e "${MAGENTA}[··] Fetching ${BOLD}${script_name}${NC}${MAGENTA}...${NC}"
+    echo -e "${CYAN}[..] Fetching ${BOLD}${script_name}${NC}${CYAN}...${NC}"
     if curl -fsSL -H "Cache-Control: no-cache" -o "${temp_file}" "${LXS_RAW_BASE}/${script_path}"; then
         echo -e "${GREEN}[OK] Payload acquired${NC}"
         chmod +x "${temp_file}"
@@ -52,16 +52,18 @@ run_sibling() {
 menu_apps() {
     while true; do
         clear
-        show_title "APPLICATIONS" "APP_REPOSITORY"
+        show_box_top "APPLICATIONS" "APP_REPOSITORY"
         echo ""
-        echo -e "  ${YELLOW}◢ 01${NC} ${GRAY}│${NC} ${WHITE}Coolify${NC}"
-        echo -e "  ${YELLOW}◢ 02${NC} ${GRAY}│${NC} ${WHITE}Pterodactyl Panel${NC}"
-        echo -e "  ${YELLOW}◢ 03${NC} ${GRAY}│${NC} ${WHITE}Uptime Kuma${NC}"
-        echo -e "  ${YELLOW}◢ 04${NC} ${GRAY}│${NC} ${WHITE}CloudPanel${NC}"
-        echo -e "  ${YELLOW}◢ 05${NC} ${GRAY}│${NC} ${WHITE}Proxmox VE Tools${NC}"
-        echo -e "  ${RED}◢ 00${NC} ${GRAY}│${NC} ${WHITE}BACK${NC}"
+        show_menu_item "01" "Coolify"
+        show_menu_item "02" "Pterodactyl Panel"
+        show_menu_item "03" "Uptime Kuma"
+        show_menu_item "04" "CloudPanel"
+        show_menu_item "05" "Proxmox VE Tools"
+        show_menu_item "00" "BACK" "" exit
         echo ""
-        echo -e -n "${YELLOW}▸${NC}${MAGENTA}_${NC} "
+        show_box_bottom
+        echo ""
+        show_prompt
         read -r choice
 
         case $choice in