Replace random string generation method with OpenSSL for better randomness in install.sh

The previous implementation using cat /dev/urandom | tr caused tr to hang and consume 100% CPU on certain environments (e.g., GCP, specific kernels) due to delayed SIGPIPE handling. Using openssl provides a finite, cryptographically secure string that eliminates this CPU spike and is noticeably faster."

install.sh

@@ -105,8 +105,10 @@ install_base() {
 
 gen_random_string() {
     local length="$1"
-    local random_string=$(LC_ALL=C tr -dc 'a-zA-Z0-9' </dev/urandom | fold -w "$length" | head -n 1)
-    echo "$random_string"
+    # openssl output base64，no need /dev/urandom + tr
+    openssl rand -base64 $(( length * 2 )) \
+        | tr -dc 'a-zA-Z0-9' \
+        | head -c "$length"
 }
     
 install_acme() {