docs(readme): update free-tier provider status for 2026

Outdated free-tier info was misleading new users. Sync corrections into
README.md and README.zh-CN.md, and force IPv4-first DNS resolution in the
CLI launcher to avoid undici IPv6 connect timeouts (502).

- Kiro AI: free tier now ~50 credits/month (was "Unlimited FREE")
- Qwen Code / Gemini CLI: free tiers discontinued in 2026
- OpenCode Free: note free model list fluctuates
- Vertex AI: Gemini API no longer uses $300 free credits since Mar 2026
- cli/cli.js: spawn server/tray with --dns-result-order=ipv4first

cli/cli.js

@@ -612,7 +612,7 @@ function startServer(updatePromise) {
   function spawnServer() {
     serverStartTime = Date.now();
     crashLog = [];
-    const child = spawn(RUNTIME, ["--max-old-space-size=6144", serverPath], {
+    const child = spawn(RUNTIME, ["--dns-result-order=ipv4first", "--max-old-space-size=6144", serverPath], {
       cwd: standaloneDir,
       stdio: showLog ? "inherit" : ["ignore", "ignore", "pipe"],
       detached: true,
@@ -785,7 +785,7 @@ function startServer(updatePromise) {
           // Windows/Linux: spawn detached bgProcess (systray works fine in child)
           console.log(`\n⏳ Starting background process... (tray icon will appear in ~3s)`);
 
-          const bgProcess = spawn(process.execPath, [__filename, "--tray", "--skip-update", "-p", port.toString()], {
+          const bgProcess = spawn(process.execPath, ["--dns-result-order=ipv4first", __filename, "--tray", "--skip-update", "-p", port.toString()], {
             detached: true,
             stdio: "ignore",
             windowsHide: true,