fix(bentopdf): create default config.json to avoid runtime 404

BentoPDF fetches /config.json at runtime. In our build/deploy flow this file
may be missing, causing noisy 404 errors in the browser console.

Create a minimal default config.json ({}), only when absent, during install
and update so custom configs are not overwritten.

ct/bentopdf.sh

@@ -51,6 +51,11 @@ function update_script() {
     export SIMPLE_MODE=true
     export VITE_USE_CDN=true
     $STD npm run build:all
+    if [[ ! -f /opt/bentopdf/dist/config.json ]]; then
+      cat <<'EOF' >/opt/bentopdf/dist/config.json
+{}
+EOF
+    fi
     msg_ok "Updated BentoPDF"
 
     msg_info "Starting Service"

install/bentopdf-install.sh

@@ -26,6 +26,11 @@ export NODE_OPTIONS="--max-old-space-size=3072"
 export SIMPLE_MODE=true
 export VITE_USE_CDN=true
 $STD npm run build:all
+if [[ ! -f /opt/bentopdf/dist/config.json ]]; then
+    cat <<'EOF' >/opt/bentopdf/dist/config.json
+{}
+EOF
+fi
 msg_ok "Setup BentoPDF"
 
 msg_info "Creating Service"