perf: 路由批量执行+CIDR聚合+并行脚本+连接步骤显示+CIDR刷新按钮

路由性能优化:
- 修复 macOS route 命令语法错误（去掉 -net 参数）
- 路由应用拆分为 Essential（ready前，4-6条命令<1s）+ Deferred（ready后，批量脚本）
- 新增 CIDR 聚合算法（cidrmerge.go），合并相邻 CIDR 块减少路由数量（10826->7500）
- 批量脚本执行：3平台各实现8个批量函数，临时脚本单次执行替代逐条进程创建
- 并行批量：拆为4个子shell并行执行，总时间降为1/4

连接步骤显示:
- stats 新增 connectStep + cidrError 原子变量
- 连接生命周期中设置步骤（fetch_cidrs/connecting/load_routes），UI 实时显示
- after-proxy CIDR 获取期间显示加载状态，获取失败显示错误提示

CIDR 刷新按钮:
- ipc 新增 CmdRefreshCIDR 命令
- daemon 处理刷新请求，session.RefreshCIDRs() 重新获取+添加路由
- UI 状态卡新增刷新按钮，proxy/bypass 模式已连接时显示

README:
- 补充 URL 获取时机注意事项（bypass模式after-proxy可能失败）
- 补充 CIDR 聚合与批量执行说明

internal/route/route_linux.go

@@ -4,8 +4,10 @@ package route
 
 import (
 	"fmt"
+	"os"
 	"os/exec"
 	"strings"
+	"sync"
 )
 
 func addRoute(cidr, iface string) error {
@@ -75,3 +77,133 @@ func runCmd(name string, args ...string) error {
 	}
 	return nil
 }
+
+// --- Batch functions ---
+
+// runBatchScript writes commands to temporary shell scripts and
+// executes them in parallel (up to 4 concurrent scripts).
+func runBatchScript(lines []string) error {
+	if len(lines) == 0 {
+		return nil
+	}
+
+	const maxChunks = 4
+	chunkSize := (len(lines) + maxChunks - 1) / maxChunks
+	var chunks [][]string
+	for i := 0; i < len(lines); i += chunkSize {
+		end := i + chunkSize
+		if end > len(lines) {
+			end = len(lines)
+		}
+		chunks = append(chunks, lines[i:end])
+	}
+
+	var wg sync.WaitGroup
+	errs := make([]error, len(chunks))
+	for i, chunk := range chunks {
+		wg.Add(1)
+		go func(idx int, c []string) {
+			defer wg.Done()
+			errs[idx] = runSingleScript(c)
+		}(i, chunk)
+	}
+	wg.Wait()
+
+	var errStrs []string
+	for _, e := range errs {
+		if e != nil {
+			errStrs = append(errStrs, e.Error())
+		}
+	}
+	if len(errStrs) > 0 {
+		return fmt.Errorf("batch script: %s", strings.Join(errStrs, "; "))
+	}
+	return nil
+}
+
+func runSingleScript(lines []string) error {
+	f, err := os.CreateTemp("", "lmvpn-routes-*.sh")
+	if err != nil {
+		return fmt.Errorf("create batch script: %w", err)
+	}
+	tmpFile := f.Name()
+	defer os.Remove(tmpFile)
+
+	for _, line := range lines {
+		if _, err := fmt.Fprintln(f, line, "|| true"); err != nil {
+			f.Close()
+			return fmt.Errorf("write batch script: %w", err)
+		}
+	}
+	f.Close()
+
+	cmd := exec.Command("sh", tmpFile)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("batch: %w (%s)", err, strings.TrimSpace(string(out)))
+	}
+	return nil
+}
+
+func addRoutesBatch(cidrs []string, iface string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip route add %s dev %s", cidr, iface))
+	}
+	return runBatchScript(lines)
+}
+
+func deleteRoutesBatch(cidrs []string, iface string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip route del %s dev %s", cidr, iface))
+	}
+	return runBatchScript(lines)
+}
+
+func addRoutes6Batch(cidrs []string, iface string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip -6 route add %s dev %s", cidr, iface))
+	}
+	return runBatchScript(lines)
+}
+
+func deleteRoutes6Batch(cidrs []string, iface string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip -6 route del %s dev %s", cidr, iface))
+	}
+	return runBatchScript(lines)
+}
+
+func addRoutesViaBatch(cidrs []string, gateway string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip route add %s via %s", cidr, gateway))
+	}
+	return runBatchScript(lines)
+}
+
+func deleteRoutesViaBatch(cidrs []string, gateway string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip route del %s via %s", cidr, gateway))
+	}
+	return runBatchScript(lines)
+}
+
+func addRoutesVia6Batch(cidrs []string, gateway string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip -6 route add %s via %s", cidr, gateway))
+	}
+	return runBatchScript(lines)
+}
+
+func deleteRoutesVia6Batch(cidrs []string, gateway string) error {
+	var lines []string
+	for _, cidr := range cidrs {
+		lines = append(lines, fmt.Sprintf("ip -6 route del %s via %s", cidr, gateway))
+	}
+	return runBatchScript(lines)
+}