fix(tdarr): use curl_with_retry and verify binaries before enabling service

Tdarr_Updater downloads the actual server/node binaries from tdarr.io at
runtime. If tdarr.io is blocked by local DNS (e.g. OPNsense OISD blocklists),
the updater exits silently with code 0, leaving no binaries on disk. The
subsequent systemctl enable then fails with 'Operation not permitted' (exit 1)
because the ExecStart paths don't exist.

Changes:
- Replace bare curl with curl_with_retry for versions.json and Tdarr_Updater.zip
  downloads to gain retry logic, DNS pre-check and exponential backoff
- Add msg_info before Tdarr_Updater run so users see this step in the log
- Check that Tdarr_Server and Tdarr_Node binaries exist after the updater
  runs; fail immediately with a clear message pointing to tdarr.io connectivity
  instead of letting systemctl fail with a confusing 'Operation not permitted'

Fixes: #13030

install/tdarr-install.sh

@@ -20,12 +20,15 @@ msg_ok "Installed Dependencies"
 msg_info "Installing Tdarr"
 mkdir -p /opt/tdarr
 cd /opt/tdarr
-RELEASE=$(curl -fsSL https://f000.backblazeb2.com/file/tdarrs/versions.json | grep -oP '(?<="Tdarr_Updater": ")[^"]+' | grep linux_x64 | head -n 1)
-curl -fsSL "$RELEASE" -o Tdarr_Updater.zip
+RELEASE=$(curl_with_retry "https://f000.backblazeb2.com/file/tdarrs/versions.json" "-" | grep -oP '(?<="Tdarr_Updater": ")[^"]+' | grep linux_x64 | head -n 1)
+curl_with_retry "$RELEASE" "Tdarr_Updater.zip"
 $STD unzip Tdarr_Updater.zip
 chmod +x Tdarr_Updater
+msg_info "Running Tdarr_Updater (downloading server/node binaries from tdarr.io)"
 $STD ./Tdarr_Updater
 rm -rf /opt/tdarr/Tdarr_Updater.zip
+[[ -f /opt/tdarr/Tdarr_Server/Tdarr_Server && -f /opt/tdarr/Tdarr_Node/Tdarr_Node ]] \
+  || fatal "Tdarr_Updater did not download server binaries — tdarr.io may be blocked by local DNS"
 msg_ok "Installed Tdarr"
 
 setup_hwaccel