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/app/api/settings/database/route.js

@@ -1,5 +1,6 @@
 import { NextResponse } from "next/server";
-import { exportDb, importDb } from "@/lib/localDb";
+import { exportDb, getSettings, importDb } from "@/lib/localDb";
+import { applyOutboundProxyEnv } from "@/lib/network/outboundProxy";
 
 export async function GET() {
   try {
@@ -15,6 +16,15 @@ export async function POST(request) {
   try {
     const payload = await request.json();
     await importDb(payload);
+
+    // Ensure proxy settings take effect immediately after a DB import.
+    try {
+      const settings = await getSettings();
+      applyOutboundProxyEnv(settings);
+    } catch (err) {
+      console.warn("[Settings][DatabaseImport] Failed to re-apply outbound proxy env:", err);
+    }
+
     return NextResponse.json({ success: true });
   } catch (error) {
     console.log("Error importing database:", error);