fix: remove openssl dependency for password generation

Use /dev/urandom instead of openssl rand for generating random
passwords. Available on all Linux/macOS systems without requiring
openssl to be installed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

installer/install.sh

@@ -135,7 +135,7 @@ prompt_yesno() {
 }
 
 generate_password() {
-  openssl rand -base64 24 | tr -d '/+=' | head -c 32
+  tr -dc 'A-Za-z0-9' < /dev/urandom | head -c 32
 }
 
 # --- Argument parsing ---
@@ -304,10 +304,6 @@ check_prerequisites() {
     log_info "Docker Compose version: $compose_version"
   fi
 
-  if ! command -v openssl >/dev/null 2>&1; then
-    log_error "OpenSSL is not installed (needed for password generation)."
-    errors=$((errors + 1))
-  fi
 
   local socket="${DOCKER_SOCKET:-$DEFAULT_DOCKER_SOCKET}"
   if [ ! -S "$socket" ]; then