refactor: replace 'let' with 'const' for better variable scoping and immutability

src/components/setting/mods/dns-viewer.tsx

@@ -379,7 +379,7 @@ export const DnsViewer = forwardRef<DialogRef>((props, ref) => {
   const formatHosts = (hosts: any): string => {
     if (!hosts || typeof hosts !== "object") return "";
 
-    let result: string[] = [];
+    const result: string[] = [];
 
     Object.entries(hosts).forEach(([domain, value]) => {
       if (Array.isArray(value)) {

src/components/setting/mods/tun-viewer.tsx

@@ -53,7 +53,7 @@ export const TunViewer = forwardRef<DialogRef>((props, ref) => {
 
   const onSave = useLockFn(async () => {
     try {
-      let tun = {
+      const tun = {
         stack: values.stack,
         device:
           values.device === ""
@@ -97,7 +97,7 @@ export const TunViewer = forwardRef<DialogRef>((props, ref) => {
             variant="outlined"
             size="small"
             onClick={async () => {
-              let tun = {
+              const tun = {
                 stack: "gvisor",
                 device: OS === "macos" ? "utun1024" : "Mihomo",
                 "auto-route": true,