feat(proxy): add outbound HTTP proxy support for OAuth + provider requests

- Patch Node fetch via undici ProxyAgent when HTTP_PROXY/HTTPS_PROXY/ALL_PROXY is set
- Ensure proxy patch is loaded for both chat pipeline and OAuth token exchange
- Add Dashboard Settings → Network to edit outbound proxy and apply immediately
- Persist outbound proxy settings in local db and initialize on server startup
- Move proxy helpers to src/lib/network/ for better structure
- Rename src/proxy.js → src/dashboardGuard.js to avoid naming confusion
- Re-apply proxy env after DB import
- Fix: close old dispatcher on proxy URL change to prevent connection pool leak
- Fix: idempotency guard to avoid patching globalThis.fetch multiple times

Made-with: Cursor

src/lib/network/proxyTest.js

@@ -0,0 +1,74 @@
+import { ProxyAgent, fetch as undiciFetch } from "undici";
+
+const DEFAULT_TEST_URL = "https://example.com/";
+const DEFAULT_TIMEOUT_MS = 8000;
+
+function normalizeString(value) {
+  if (value === undefined || value === null) return "";
+  return String(value).trim();
+}
+
+export async function testProxyUrl({ proxyUrl, testUrl, timeoutMs } = {}) {
+  const normalizedProxyUrl = normalizeString(proxyUrl);
+  if (!normalizedProxyUrl) {
+    return { ok: false, status: 400, error: "proxyUrl is required" };
+  }
+
+  const normalizedTestUrl = normalizeString(testUrl) || DEFAULT_TEST_URL;
+  const timeoutMsRaw = Number(timeoutMs);
+  const normalizedTimeoutMs =
+    Number.isFinite(timeoutMsRaw) && timeoutMsRaw > 0
+      ? Math.min(timeoutMsRaw, 30000)
+      : DEFAULT_TIMEOUT_MS;
+
+  let dispatcher;
+
+  try {
+    try {
+      dispatcher = new ProxyAgent({ uri: normalizedProxyUrl });
+    } catch (err) {
+      return {
+        ok: false,
+        status: 400,
+        error: `Invalid proxy URL: ${err?.message || String(err)}`,
+      };
+    }
+
+    const controller = new AbortController();
+    const startedAt = Date.now();
+    const timer = setTimeout(() => controller.abort(), normalizedTimeoutMs);
+
+    try {
+      const res = await undiciFetch(normalizedTestUrl, {
+        method: "HEAD",
+        dispatcher,
+        signal: controller.signal,
+        headers: {
+          "User-Agent": "9Router",
+        },
+      });
+
+      return {
+        ok: res.ok,
+        status: res.status,
+        statusText: res.statusText,
+        url: normalizedTestUrl,
+        elapsedMs: Date.now() - startedAt,
+      };
+    } catch (err) {
+      const message =
+        err?.name === "AbortError"
+          ? "Proxy test timed out"
+          : err?.message || String(err);
+      return { ok: false, status: 500, error: message };
+    } finally {
+      clearTimeout(timer);
+    }
+  } finally {
+    try {
+      await dispatcher?.close?.();
+    } catch {
+      // ignore
+    }
+  }
+}