Remove legacy vpn proxy code and simplify the client

test/server/singbox-gateway-mode.test.js

@@ -0,0 +1,33 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import test from 'node:test';
+
+process.env.APP_MODE = 'gateway';
+process.env.DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), 'vpn-proxy-gateway-test-'));
+process.env.SING_BOX_CACHE = path.join(process.env.DATA_DIR, 'cache.db');
+
+const { buildGatewayConfig } = await import(`../../src/server/singbox.js?gateway=${Date.now()}`);
+
+const subscriptionConfig = {
+  outbounds: [{
+    type: 'vless',
+    tag: 'test-vpn',
+    server: 'vpn.example.test',
+    server_port: 443,
+    uuid: '00000000-0000-4000-8000-000000000000',
+    tls: { enabled: true },
+  }],
+};
+
+test('gateway routes transparent and proxy traffic only through the selected VPN', () => {
+  const config = buildGatewayConfig(subscriptionConfig, 'test-vpn');
+
+  assert.deepEqual(config.route.rule_set, []);
+  assert.deepEqual(config.route.rules, [
+    { inbound: ['tproxy-in'], outbound: 'test-vpn' },
+    { inbound: ['mixed-in'], outbound: 'test-vpn' },
+  ]);
+  assert.equal(config.route.final, 'test-vpn');
+});