Prefer silent mode on PHS env conflict

When PHS_SILENT and PHS_VERBOSE are both set, stop falling back to interactive mode. Changes prefer silent mode to keep automation safe and avoid blocking unattended/non-TTY updates. Only show a whiptail warning when both stdin/stdout are TTYs and whiptail is present, and ignore any whiptail errors. Added a brief comment and adjusted the fallback message accordingly.

misc/build.func

@@ -3520,10 +3520,14 @@ msg_menu() {
 # ------------------------------------------------------------------------------
 resolve_phs_mode() {
   if [[ -n "${PHS_SILENT+x}" ]] && [[ "${PHS_SILENT}" == "1" ]] && [[ -n "${PHS_VERBOSE+x}" ]] && [[ "${PHS_VERBOSE}" == "1" ]]; then
-    whiptail --backtitle "Proxmox VE Helper Scripts" \
-      --title "⚠️ Configuration Conflict Warning" \
-      --msgbox "PHS_SILENT and PHS_VERBOSE environment variables are both set.\n\nFalling back to interactive mode." 10 58
-    PHS_MODE="interactive"
+    # Conflict handling must never block unattended/non-TTY updates.
+    # Prefer silent mode to keep automation safe.
+    if [[ -t 0 ]] && [[ -t 1 ]] && command -v whiptail >/dev/null 2>&1; then
+      whiptail --backtitle "Proxmox VE Helper Scripts" \
+        --title "Configuration Conflict Warning" \
+        --msgbox "PHS_SILENT and PHS_VERBOSE are both set.\n\nFalling back to silent mode." 10 58 || true
+    fi
+    PHS_MODE="silent"
   elif [[ -n "${PHS_SILENT+x}" ]] && [[ "${PHS_SILENT}" == "1" ]]; then
     PHS_MODE="silent"
   elif [[ -n "${PHS_VERBOSE+x}" ]] && [[ "${PHS_VERBOSE}" == "1" ]]; then