fix(droplet): Use awk for lowercase instead of buggy BusyBox tr

BusyBox tr '[:upper:]' '[:lower:]' has a bug that converts 'p' to 'w',
causing .zip to be detected as .ziw. Use awk tolower() instead.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package/secubox/secubox-app-droplet/files/usr/sbin/dropletctl

@@ -75,8 +75,8 @@ cmd_publish() {
     log_info "Publishing: $file as $vhost"
 
     # Detect file type by extension (file command not available on OpenWrt)
-    # Strip any CR/LF that may come from Windows uploads or JSON parsing
-    local file_ext=$(echo "$file" | sed 's/.*\.//' | tr '[:upper:]' '[:lower:]' | tr -d '\r\n')
+    # Use awk for lowercase - BusyBox tr '[:upper:]' '[:lower:]' is buggy
+    local file_ext=$(echo "$file" | sed 's/.*\.//' | awk '{print tolower($0)}' | tr -d '\r\n')
 
     if [ "$file_ext" = "zip" ]; then
         log_info "Extracting ZIP..."