docmost: stop corepack asking for confirmation during the build (#17282)

Docmost pins its package manager, so running pnpm goes through corepack,
which asks before fetching the pinned version:

  Corepack is about to download .../pnpm-11.25.0.tgz
  ? Do you want to continue? [Y/n]

The pnpm calls run under $STD, so with verbose off the question is
never shown and the update sits on "Configuring Docmost" waiting for an
answer nobody can see. With verbose on the same update completes,
because the prompt is visible and gets answered, which is exactly what
the reporter observed.

Set COREPACK_ENABLE_DOWNLOAD_PROMPT=0 before the pnpm calls in both the
install and the update, the way fifteen other ct scripts and ten
install scripts already do.

ct/docmost.sh

@@ -57,6 +57,7 @@ function update_script() {
 
     msg_info "Configuring Docmost"
     cd /opt/docmost
+    export COREPACK_ENABLE_DOWNLOAD_PROMPT=0
     $STD pnpm install --force
     $STD pnpm build
     msg_ok "Configured Docmost"

install/docmost-install.sh

@@ -48,6 +48,7 @@ sed -i -e "s|APP_SECRET=.*|APP_SECRET=$(openssl rand -base64 32 | tr -dc 'a-zA-Z
   -e "s|^STORAGE_DRIVER=azure|#STORAGE_DRIVER=azure|" \
   /opt/docmost/.env
 export NODE_OPTIONS="--max-old-space-size=2048"
+export COREPACK_ENABLE_DOWNLOAD_PROMPT=0
 $STD pnpm install
 $STD pnpm build
 msg_ok "Configured Docmost"