[management,client] Default to NetBird's upload service when nothing is configured

The previous commit made a peer with no destination — no MDM override, no URL
named by the caller, nothing published by its management server — refuse to
upload and keep the bundle local unless it was enrolled with NetBird's cloud.
That closed the reported data-boundary concern, but it broke the default for
everyone who uploads a bundle as part of their day: a self-hosted user opening
a support ticket got a refusal where the command used to work.

Product decision (NetBird's, not the reporter's): the knob to keep bundles
inside your own infrastructure is what this branch provides, and it is enough.
The default stays the service NetBird runs, self-hosted included. An admin who
needs the bundles to stay in-house configures the destination; until then the
everyday flow keeps working.

So ResolveUploadURL drops the cloud check, the sentinel error and the
managementURL argument, and never fails:

    MDM  >  explicitly named URL  >  published by management  >  NetBird's service

Nothing observable changes for a deployment that configures nothing, which also
removes two edge cases the fail-closed default had: a peer still enrolled on the
legacy api.wiretrustee.com host would have been classified self-hosted and
refused, and an upgrade would have silently stopped uploads for self-hosted
deployments relying on them. The privilege gate is unaffected — a host other
than the default one still requires a privileged caller, so pointing the CLI
somewhere other than what management published needs root.

management/internals/server/config/config.go

@@ -218,12 +218,11 @@ type AgentNetwork struct {
 //
 // The client paths that upload without a human picking a destination — the
 // remote debug-bundle job, the mobile clients and the desktop UI — take the
-// destination from here. It exists so a self-hosted deployment keeps its
-// bundles, which carry peer logs, routes, DNS and firewall state, inside the
-// operator's own control sphere instead of reaching the upload service NetBird
-// runs. Leaving it unset publishes no destination: a peer enrolled with
-// NetBird's cloud still uses NetBird's service, a self-hosted peer keeps the
-// bundle local.
+// destination from here. It exists so an operator who needs the bundles, which
+// carry peer logs, routes, DNS and firewall state, to stay inside their own
+// infrastructure can say so once. Leaving it unset publishes no destination and
+// the peers upload to the service NetBird runs, which keeps the everyday
+// "collect a bundle and send it to support" flow working out of the box.
 //
 // Set URL to the upload service's get-URL endpoint, e.g.
 // https://upload.example.com/upload-url (see the upload-server component).

management/internals/shared/grpc/conversion.go

@@ -115,9 +115,10 @@ func toNetbirdConfig(config *nbconfig.Config, turnCredentials *Token, relayToken
 		}
 	}
 
-	// The account setting wins, the server config is the deployment-wide default
-	// a self-hosted install can set once so a fresh account is not left with the
-	// vendor fallback. Both are https-validated where they are written.
+	// The account setting wins, the server config is the deployment-wide value a
+	// self-hosted install can set once for every account. Both are
+	// https-validated where they are written. Neither set publishes nothing, and
+	// the peers fall back to the service NetBird runs.
 	debugUploadURL := config.DebugUpload.URL
 	if settings != nil && settings.DebugBundleUploadURL != "" {
 		debugUploadURL = settings.DebugBundleUploadURL

management/server/types/settings.go

@@ -79,10 +79,9 @@ type Settings struct {
 	// DebugBundleUploadURL is the debug-bundle upload service the peers of this
 	// account send their bundles to. A bundle carries peer logs, routes, DNS and
 	// firewall state, so the destination decides whose infrastructure that data
-	// lands on; setting it keeps a self-hosted account's bundles inside its own
-	// control sphere. Empty falls back to the deployment-wide DebugUpload.URL
-	// from the management server config, and with neither only a peer enrolled
-	// with NetBird's cloud uploads at all. Must be an https URL with a host.
+	// lands on. Empty falls back to the deployment-wide DebugUpload.URL from the
+	// management server config, and with neither to the service NetBird runs.
+	// Must be an https URL with a host.
 	DebugBundleUploadURL string
 
 	// AgentNetworkOnly limits the dashboard to the Agent Network surface for this account.