优化安装逻辑

.env.example

@@ -0,0 +1,4 @@
+# sing-box Xboard Node Configuration
+PANEL_URL=https://your-panel.com
+PANEL_TOKEN=your_node_key
+NODE_ID=1

install.sh

@@ -113,10 +113,21 @@ build_sing_box() {
 install_go
 build_sing_box
 
+# Load .env if exists
+if [[ -f ".env" ]]; then
+    echo -e "${YELLOW}Loading configuration from .env...${NC}"
+    source .env
+fi
+
 # Interactive Prompts
-read -p "Enter Panel URL (e.g., https://yourbase.com): " PANEL_URL
-read -p "Enter Node ID: " NODE_ID
-read -p "Enter Panel Token (Node Key): " PANEL_TOKEN
+read -p "Enter Panel URL [${PANEL_URL}]: " INPUT_URL
+PANEL_URL=${INPUT_URL:-$PANEL_URL}
+
+read -p "Enter Node ID [${NODE_ID}]: " INPUT_ID
+NODE_ID=${INPUT_ID:-$NODE_ID}
+
+read -p "Enter Panel Token (Node Key) [${PANEL_TOKEN}]: " INPUT_TOKEN
+PANEL_TOKEN=${INPUT_TOKEN:-$PANEL_TOKEN}
 
 if [[ -z "$PANEL_URL" || -z "$NODE_ID" || -z "$PANEL_TOKEN" ]]; then
     echo -e "${RED}All fields are required!${NC}"