[management,client] Take the debug-bundle upload destination from management

The debug-bundle paths that upload without a human picking a destination
compiled the vendor endpoint in: the mobile clients and the desktop UI hold
`https://upload.debug.netbird.io/upload-url` as a constant, the CLI defaults its
flag to it, and the remote job falls back to it when nothing else is set. A
self-hosted deployment therefore shipped peer logs, routes, DNS and firewall
state to NetBird-run infrastructure without its operator ever configuring that,
and had no way to point those paths anywhere else. #7147 and #7153 gave the
remote job a per-job URL and an MDM override, but neither reaches the mobile,
UI or CLI paths, and both fail open when unset.

Publish the destination from the management server instead, on the channel that
already carries stun/turn/signal/relay/flow/metrics:

- `NetbirdConfig.debug.upload_url`, sourced from the new account setting
  `debug_bundle_upload_url` (REST + dashboard) and falling back to the new
  `DebugUpload.URL` in the management server config, which a self-hosted install
  can set once so a fresh account is not left on the vendor default. Both are
  validated as https-with-host where they are written; a change fans out to
  connected peers rather than waiting for the next login.
- One resolver on the client, `debug.ResolveUploadURL`, used by every path:
  MDM override > explicitly named URL > destination published by management >
  the NetBird service, but only for a peer enrolled with NetBird's cloud.
  Anything else fails closed with ErrNoUploadDestination and the bundle stays
  local, which is the behaviour change: a self-hosted deployment that names no
  upload service no longer uploads at all.
- The engine keeps the published value (`Engine.DebugUploadURL`) so the bundle
  paths, which run off the engine loop, do not have to read it back out of the
  opt-in sync-response store.
- The daemon request grows `upload`, so "upload to wherever this deployment
  says" is expressible; an empty `uploadURL` no longer has to mean "no upload".
  The privilege gate is unchanged and still applies only to a URL the local
  caller named — a destination published by management is the operator naming
  their own service.
- The desktop UI stops carrying a vendor URL of its own and sends the intent.

Reported privately as GHSA-hf99-43rj-h577.

client/server/debug.go

@@ -35,35 +35,46 @@ func (s *Server) DebugBundle(callerCtx context.Context, req *proto.DebugBundleRe
 	// socket that carries no identity, which skips the UI log.
 	callerID, callerIdentified := ipcauth.CallerIdentity(callerCtx)
 
-	path, managementURL, err := s.generateDebugBundle(req, uiLogOpener(callerID, callerIdentified))
+	path, managementURL, publishedUploadURL, err := s.generateDebugBundle(req, uiLogOpener(callerID, callerIdentified))
 	if err != nil {
 		return nil, err
 	}
 
-	if req.GetUploadURL() == "" {
+	if !req.GetUpload() && req.GetUploadURL() == "" {
 		return &proto.DebugBundleResponse{Path: path}, nil
 	}
 
+	// The destination the management server publishes needs no privilege check:
+	// it is the operator of this deployment naming their own upload service, and
+	// the peer already trusts that server for its whole configuration. Only a
+	// URL the local caller named goes through requirePrivilegeForUploadURL above.
+	uploadURL, err := debug.ResolveUploadURL(req.GetUploadURL(), publishedUploadURL, managementURL)
+	if err != nil {
+		log.Errorf("cannot upload debug bundle: %v", err)
+		return &proto.DebugBundleResponse{Path: path, UploadFailureReason: err.Error()}, nil
+	}
+
 	// The upload runs without s.mutex held: it does network I/O to a possibly
 	// slow destination and must not block the other RPCs that take the lock. The
 	// bounded context is a backstop against a hung connection.
 	uploadCtx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
 	defer cancel()
-	key, err := debug.UploadDebugBundle(uploadCtx, req.GetUploadURL(), managementURL, path, req.GetUploadInsecure())
+	key, err := debug.UploadDebugBundle(uploadCtx, uploadURL, managementURL, path, req.GetUploadInsecure())
 	if err != nil {
-		log.Errorf("failed to upload debug bundle to %s: %v", req.GetUploadURL(), err)
+		log.Errorf("failed to upload debug bundle to %s: %v", uploadURL, err)
 		return &proto.DebugBundleResponse{Path: path, UploadFailureReason: err.Error()}, nil
 	}
 
-	log.Infof("debug bundle uploaded to %s with key %s", req.GetUploadURL(), key)
+	log.Infof("debug bundle uploaded to %s with key %s", uploadURL, key)
 
 	return &proto.DebugBundleResponse{Path: path, UploadedKey: key}, nil
 }
 
 // generateDebugBundle builds the bundle under s.mutex and returns its path plus
-// the management URL captured under the lock, so the caller can run the upload
-// without holding the lock.
-func (s *Server) generateDebugBundle(req *proto.DebugBundleRequest, uiOpener debug.LogOpener) (path string, managementURL string, err error) {
+// the management URL and the upload service the management server publishes,
+// both captured under the lock, so the caller can run the upload without
+// holding the lock.
+func (s *Server) generateDebugBundle(req *proto.DebugBundleRequest, uiOpener debug.LogOpener) (path string, managementURL string, publishedUploadURL string, err error) {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 
@@ -78,6 +89,7 @@ func (s *Server) generateDebugBundle(req *proto.DebugBundleRequest, uiOpener deb
 			if cm := engine.GetClientMetrics(); cm != nil {
 				clientMetrics = cm
 			}
+			publishedUploadURL = engine.DebugUploadURL()
 		}
 	}
 
@@ -131,14 +143,14 @@ func (s *Server) generateDebugBundle(req *proto.DebugBundleRequest, uiOpener deb
 
 	path, err = bundleGenerator.Generate()
 	if err != nil {
-		return "", "", fmt.Errorf("generate debug bundle: %w", err)
+		return "", "", "", fmt.Errorf("generate debug bundle: %w", err)
 	}
 
 	if s.config != nil && s.config.ManagementURL != nil {
 		managementURL = s.config.ManagementURL.String()
 	}
 
-	return path, managementURL, nil
+	return path, managementURL, publishedUploadURL, nil
 }
 
 // GetLogLevel gets the current logging level for the server.