ci(smoke): retry transient GitHub download failures

The first-boot smoke test and install.sh fetched the released binary with
a single curl attempt, so a transient GitHub/CDN 504 failed the whole job.

- smoke-firstboot.sh: add --retry/--retry-all-errors with connect/max
  timeouts to the version API and tarball downloads, split the download
  into a guarded step, and assert the tarball is non-empty.
- install.sh: add --retry plus connect/max timeouts to the release-binary
  downloads and version lookups. Omit --retry-all-errors here for curl
  < 7.71 (Ubuntu 20.04 / Debian 10 / CentOS 7) compatibility; plain
  --retry already covers 504 and other transient errors.

install.sh

@@ -1305,17 +1305,17 @@ install_x-ui() {
 
     # Download resources
     if [ $# == 0 ]; then
-        tag_version=$(curl -Ls "https://api.github.com/repos/MHSanaei/3x-ui/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/')
+        tag_version=$(curl -Ls --retry 5 --retry-delay 3 --connect-timeout 15 --max-time 60 "https://api.github.com/repos/MHSanaei/3x-ui/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/')
         if [[ ! -n "$tag_version" ]]; then
             echo -e "${yellow}Trying to fetch version with IPv4...${plain}"
-            tag_version=$(curl -4 -Ls "https://api.github.com/repos/MHSanaei/3x-ui/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/')
+            tag_version=$(curl -4 -Ls --retry 5 --retry-delay 3 --connect-timeout 15 --max-time 60 "https://api.github.com/repos/MHSanaei/3x-ui/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/')
             if [[ ! -n "$tag_version" ]]; then
                 echo -e "${red}Failed to fetch x-ui version, it may be due to GitHub API restrictions, please try it later${plain}"
                 exit 1
             fi
         fi
         echo -e "Got x-ui latest version: ${tag_version}, beginning the installation..."
-        curl -4fLRo ${xui_folder}-linux-$(arch).tar.gz https://github.com/MHSanaei/3x-ui/releases/download/${tag_version}/x-ui-linux-$(arch).tar.gz
+        curl -4fLR --retry 5 --retry-delay 3 --connect-timeout 15 --max-time 300 -o ${xui_folder}-linux-$(arch).tar.gz https://github.com/MHSanaei/3x-ui/releases/download/${tag_version}/x-ui-linux-$(arch).tar.gz
         if [[ $? -ne 0 ]]; then
             echo -e "${red}Downloading x-ui failed, please be sure that your server can access GitHub ${plain}"
             exit 1
@@ -1332,7 +1332,7 @@ install_x-ui() {
 
         url="https://github.com/MHSanaei/3x-ui/releases/download/${tag_version}/x-ui-linux-$(arch).tar.gz"
         echo -e "Beginning to install x-ui $1"
-        curl -4fLRo ${xui_folder}-linux-$(arch).tar.gz ${url}
+        curl -4fLR --retry 5 --retry-delay 3 --connect-timeout 15 --max-time 300 -o ${xui_folder}-linux-$(arch).tar.gz ${url}
         if [[ $? -ne 0 ]]; then
             echo -e "${red}Download x-ui $1 failed, please check if the version exists ${plain}"
             exit 1