Replace illegible box-art banner with readable gradient-bar banner

The Unicode box-drawing art didn't form legible letters. Now uses
two rainbow gradient bars around a plain, readable title + subtitle.

Co-Authored-By: Claude <noreply@anthropic.com>

cleanup-server

@@ -18,36 +18,38 @@ else
 fi
 
 # -----------------------------
-# Banner rainbow (giống style `cleanup`)
+# Banner rainbow nhưng đọc được: thanh gradient + tiêu đề rõ
 # -----------------------------
-print_banner() {
-    local use_color=0 reset="" i=0 line
-    local -a lines=(
-        '  ██████╗██╗   ██╗ ██████╗██╗  ██╗██╗   ██╗██████╗  ███████╗███╗   ██╗ ██████╗██╗  ██╗'
-        ' ██╔════╝██║   ██║██╔════╝██║  ██║██║   ██║██╔══██╗ ██╔════╝████╗  ██║██╔═══██╗╚██╗██╔╝'
-        ' ██║     ██║   ██║██║     ███████║██║   ██║██║  ██║ █████╗  ██╔██╗ ██║██║   ██║ ╚███╔╝ '
-        ' ██║     ██║   ██║██║     ██╔══██║██║   ██║██║  ██║ ██╔══╝  ██║╚██╗██║██║   ██║ ██╔██╗ '
-        ' ╚██████╗╚██████╔╝╚██████╗██║  ██║╚██████╔╝██████╔╝ ███████╗██║ ╚████║╚██████╔╝██╔╝ ██╗'
-        '  ╚═════╝ ╚═════╝  ╚═════╝╚═╝  ╚═╝ ╚═════╝ ╚═════╝  ╚══════╝╚═╝  ╚═══╝ ╚═════╝ ╚═╝  ╚═╝'
-    )
-    local -a colors=()
+repeat_char() {
+    # $1 = số lượng, $2 = ký tự
+    printf "%${1}s" "" | tr ' ' "$2"
+}
+
+# In 1 thanh block gradient rainbow (TTY) hoặc '#' (non-TTY)
+rainbow_bar() {
+    local width="$1"
     if [ -t 1 ]; then
-        use_color=1
-        reset=$'\033[0m'
-        colors=(
-            $'\033[1;38;5;51m' $'\033[1;38;5;87m' $'\033[1;38;5;123m'
-            $'\033[1;38;5;159m' $'\033[1;38;5;220m' $'\033[1;38;5;214m'
-        )
+        local -a codes=(51 87 123 159 220 214 209 204)
+        local n=${#codes[@]} seg i line=""
+        for ((i = 0; i < n; i++)); do
+            seg=$(( (width + n - 1 - i) / n ))
+            line+="$(printf '\033[1;38;5;%dm' "${codes[$i]}")""$(repeat_char "$seg" "█")"
+        done
+        printf '%s%s\n' "$line" "$C_RESET"
+    else
+        repeat_char "$width" "#"
+        echo
     fi
+}
+
+print_banner() {
     echo ""
-    for line in "${lines[@]}"; do
-        if [ "$use_color" -eq 1 ]; then
-            printf '%b%s%b\n' "${colors[$i]}" "$line" "$reset"
-        else
-            printf '%s\n' "$line"
-        fi
-        i=$((i + 1))
-    done
+    rainbow_bar 56
+    echo ""
+    printf '  %s🧹  CLEANUP-SERVER%s\n' "$C_TITLE" "$C_RESET"
+    printf '  %sDọn dẹp + nâng cấp server (Ubuntu / Arch)%s\n' "$C_WARN" "$C_RESET"
+    echo ""
+    rainbow_bar 56
     echo ""
 }