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

lxs.sh

@@ -120,15 +120,7 @@ check_remote_version() {
 }
 
 show_lxs_logo() {
-    local cols head tail_len
-    cols=$(tput cols 2>/dev/null || echo 64)
-    head=" L X S // v${LXS_VERSION} "
-    tail_len=$(( cols - ${#head} - 12 ))
-    [ "$tail_len" -lt 4 ] && tail_len=4
-    local bar
-    bar=$(printf '▀%.0s' $(seq 1 "$tail_len"))
-    echo ""
-    echo -e "${YELLOW}▀▀▀${WHITE}${BOLD}${head}${NC}${YELLOW}${bar}${NC} ${GREEN}[ONLINE]${NC}"
+    show_box_top "LXS // v${LXS_VERSION}" "ONLINE"
 }
 
 show_header() {
@@ -136,7 +128,8 @@ show_header() {
     show_lxs_logo
 
     if [ "${LXS_UPDATE_AVAILABLE:-0}" = "1" ]; then
-        echo -e "${YELLOW}▲ UPDATE_AVAILABLE :: v${LXS_REMOTE_VERSION}${NC}  ${GRAY}// run \`lxs update\`${NC}"
+        echo ""
+        echo -e "  ${CYAN}[!!] UPDATE_AVAILABLE${NC}  ${WHITE}v${LXS_REMOTE_VERSION}${NC}  ${GRAY}// run \`lxs update\`${NC}"
     fi
 
     local hostname os_version kernel uptime_info ip_address cpu_cores total_mem used_mem disk_usage
@@ -151,10 +144,10 @@ show_header() {
     disk_usage=$(df -h / | awk 'NR==2 {print $3 "/" $2 " (" $5 ")"}')
 
     echo ""
-    printf "  ${CYAN}NODE${NC}  %-22s ${CYAN}KERN${NC}  %s\n" "$hostname" "$kernel"
-    printf "  ${CYAN}ADDR${NC}  %-22s ${CYAN}UP${NC}    %s\n" "$ip_address" "$uptime_info"
-    printf "  ${CYAN}OS${NC}    %-22s ${CYAN}CPU${NC}   %s cores\n" "$os_version" "$cpu_cores"
-    printf "  ${CYAN}DISK${NC}  %-22s ${CYAN}MEM${NC}   %s / %s\n" "$disk_usage" "$used_mem" "$total_mem"
+    printf "  ${CYAN}NODE${NC}  ${WHITE}%-26s${NC}  ${CYAN}KERN${NC}  ${WHITE}%s${NC}\n" "$hostname" "$kernel"
+    printf "  ${CYAN}ADDR${NC}  ${WHITE}%-26s${NC}  ${CYAN}UP${NC}    ${WHITE}%s${NC}\n" "$ip_address" "$uptime_info"
+    printf "  ${CYAN}OS${NC}    ${WHITE}%-26s${NC}  ${CYAN}CPU${NC}   ${WHITE}%s cores${NC}\n" "$os_version" "$cpu_cores"
+    printf "  ${CYAN}DISK${NC}  ${WHITE}%-26s${NC}  ${CYAN}MEM${NC}   ${WHITE}%s / %s${NC}\n" "$disk_usage" "$used_mem" "$total_mem"
     echo ""
 }
 
@@ -197,7 +190,7 @@ download_and_run() {
     temp_file=$(mktemp "/tmp/lxs.${script_name%.*}.XXXXXX.sh")
 
     echo ""
-    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 "${temp_file}" \
@@ -304,7 +297,7 @@ lxs_sync_install() {
     }
     trap 'rm -rf "$work"' RETURN
 
-    echo -e "${MAGENTA}[··] Fetching ${LXS_TARBALL_URL}...${NC}"
+    echo -e "${CYAN}[..] Fetching ${LXS_TARBALL_URL}...${NC}"
     if ! curl -fsSL -H "Cache-Control: no-cache" -o "${work}/lxs.tgz" "$LXS_TARBALL_URL"; then
         echo -e "${RED}[KO] Download failed${NC}"
         return 1
@@ -372,18 +365,18 @@ cmd_install_self() {
 main_menu() {
     check_os
     check_remote_version
-    local hostname
-    hostname=$(hostname 2>/dev/null || echo "${HOSTNAME:-node}")
     while true; do
         show_header
-        echo -e "${MAGENTA}>> SELECT_PROTOCOL <<${NC}"
+        show_box_mid "SELECT"
         echo ""
-        echo -e "  ${YELLOW}◢ 01${NC} ${GRAY}│${NC} ${WHITE}APPLICATIONS${NC}    ${GRAY}// deploy stacks${NC}"
-        echo -e "  ${YELLOW}◢ 02${NC} ${GRAY}│${NC} ${WHITE}TOOLS${NC}           ${GRAY}// sysadmin daemons${NC}"
-        echo -e "  ${YELLOW}◢ UU${NC} ${GRAY}│${NC} ${WHITE}FETCH_UPDATE${NC}    ${GRAY}// sync remote${NC}"
-        echo -e "  ${RED}◢ 00${NC} ${GRAY}│${NC} ${WHITE}JACK_OUT${NC}        ${GRAY}// exit shell${NC}"
+        show_menu_item "01" "APPLICATIONS" "deploy stacks"
+        show_menu_item "02" "TOOLS"        "sysadmin daemons"
+        show_menu_item "UU" "FETCH_UPDATE" "sync remote"
+        show_menu_item "00" "JACK_OUT"     "exit shell" exit
         echo ""
-        echo -e -n "${MAGENTA}jack_in${NC}@${CYAN}${hostname}${NC} ${YELLOW}▸${NC}${MAGENTA}_${NC} "
+        show_box_bottom
+        echo ""
+        show_prompt
         read -r choice
 
         case $choice in
@@ -399,7 +392,7 @@ main_menu() {
             0|00)
                 clear
                 show_lxs_logo
-                echo -e "${MAGENTA}JACK_OUT${NC} ${GRAY}// session terminated${NC}\n"
+                echo -e "${CYAN}JACK_OUT${NC} ${GRAY}// session terminated${NC}\n"
                 exit 0
                 ;;
             *) echo -e "${RED}[KO] Invalid protocol.${NC}"; sleep 1 ;;