fix(clouddrop): cap concurrent TCP connections at 50 via undici Agent

Defensive guard to stay under server's cd_conn 100/IP limit even
with aggressive parallel uploads and keep-alive pooling.

lib/clouddrop-upload.js

@@ -1,7 +1,7 @@
 const fs = require('fs');
 const path = require('path');
 const crypto = require('crypto');
-const { request } = require('undici');
+const { request, Agent } = require('undici');
 
 const BASE_URL = 'https://clouddrop.cc';
 const API_BASE = `${BASE_URL}/api/cloud`;
@@ -15,6 +15,16 @@ const COMPLETE_TIMEOUT = 5 * 60_000;
 const SHARE_TIMEOUT = 30_000;
 const SIMPLE_UPLOAD_TIMEOUT = 30 * 60_000;
 
+// Cap concurrent TCP connections to clouddrop.cc at 50 to stay well under
+// the server's per-IP limit of 100 concurrent connections (cd_conn).
+// Shared across all ClouddropUploader instances via module-level agent.
+const clouddropAgent = new Agent({
+  connections: 50,
+  pipelining: 1,
+  keepAliveTimeout: 30_000,
+  keepAliveMaxTimeout: 60_000
+});
+
 /**
  * Clouddrop.cc uploader — uses API Key (Bearer) authentication.
  * Files > 16 MB use the chunked protocol, smaller files use simple upload.
@@ -115,6 +125,7 @@ class ClouddropUploader {
 
     const res = await request(`${API_BASE}/upload?mode=rename`, {
       method: 'POST',
+      dispatcher: clouddropAgent,
       body: generate(),
       signal,
       headers: this._headers({
@@ -138,6 +149,7 @@ class ClouddropUploader {
     // 1. Init session
     const initRes = await request(`${API_BASE}/upload/init`, {
       method: 'POST',
+      dispatcher: clouddropAgent,
       signal,
       headers: this._headers({ 'Content-Type': 'application/json' }),
       body: JSON.stringify({ filename: fileName, size: fileSize, parentId: null }),
@@ -167,6 +179,7 @@ class ClouddropUploader {
 
         const chunkRes = await request(`${API_BASE}/upload/${sessionId}/chunk/${i}`, {
           method: 'PUT',
+          dispatcher: clouddropAgent,
           signal,
           body: buf,
           headers: this._headers({
@@ -188,6 +201,7 @@ class ClouddropUploader {
     // 3. Complete session
     const completeRes = await request(`${API_BASE}/upload/${sessionId}/complete`, {
       method: 'POST',
+      dispatcher: clouddropAgent,
       signal,
       headers: this._headers({ 'Content-Type': 'application/json' }),
       body: '{}',
@@ -206,6 +220,7 @@ class ClouddropUploader {
   async _createShareLink(fileId, signal) {
     const res = await request(`${API_BASE}/share-link`, {
       method: 'POST',
+      dispatcher: clouddropAgent,
       signal,
       headers: this._headers({ 'Content-Type': 'application/json' }),
       body: JSON.stringify({ fileId, expiry: 'never' }),
@@ -223,6 +238,7 @@ class ClouddropUploader {
     if (!this.apiKey) throw new Error('Clouddrop: API-Key fehlt');
     const res = await request(`${API_BASE}/files?limit=1`, {
       method: 'GET',
+      dispatcher: clouddropAgent,
       signal,
       headers: this._headers(),
       headersTimeout: 15_000,