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/initOutboundProxy.js

@@ -0,0 +1,22 @@
+import { getSettings } from "@/lib/localDb";
+import { applyOutboundProxyEnv } from "@/lib/network/outboundProxy";
+
+let initialized = false;
+
+export async function ensureOutboundProxyInitialized() {
+  if (initialized) return true;
+
+  try {
+    const settings = await getSettings();
+    applyOutboundProxyEnv(settings);
+    initialized = true;
+  } catch (error) {
+    console.error("[ServerInit] Error initializing outbound proxy:", error);
+  }
+
+  return initialized;
+}
+
+ensureOutboundProxyInitialized().catch(console.log);
+
+export default ensureOutboundProxyInitialized;