[client] Keep file drop out of the wasm build

File drop needs a local filesystem to deliver into and a receiver it can bind,
so wasm supports neither and never sets a manager. The code still linked in,
because the Engine reached filedrop through an untagged field, and with it the
net/http server and client. That put the wasm binary 0.97MiB over the 60MB
budget, on a main that had 0.34MiB of headroom left.

Split the feature on the js tag: the logic file and the OS dialer become !js,
a js no-op carries the start, stop and rebind entry points the engine calls on
its lifecycle paths, and a build-tagged alias types the manager so engine.go
and connect.go stay untagged and lose the import. iOS keeps the full feature:
the logic file is !js and the iOS dialer stays behind the ios tag.

Drops the wasm binary to 59.89MiB, with no filedrop symbol left in it.

client/internal/connect.go

@@ -27,7 +27,6 @@ import (
 	"github.com/netbirdio/netbird/client/iface/device"
 	"github.com/netbirdio/netbird/client/iface/netstack"
 	"github.com/netbirdio/netbird/client/internal/dns"
-	"github.com/netbirdio/netbird/client/internal/filedrop"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
 	"github.com/netbirdio/netbird/client/internal/listener"
 	"github.com/netbirdio/netbird/client/internal/metrics"
@@ -70,7 +69,7 @@ type ConnectClient struct {
 	engineMutex     sync.Mutex
 	clientMetrics   *metrics.ClientMetrics
 	updateManager   *updater.Manager
-	fileDropManager *filedrop.Manager
+	fileDropManager fileDropManager
 
 	persistSyncResponse bool
 
@@ -117,7 +116,7 @@ func (c *ConnectClient) SetUpdateManager(um *updater.Manager) {
 
 // SetFileDropManager hands the engine the active profile's file drop manager, so
 // the transfer receiver starts and stops with the tunnel. Must be set before Run.
-func (c *ConnectClient) SetFileDropManager(m *filedrop.Manager) {
+func (c *ConnectClient) SetFileDropManager(m fileDropManager) {
 	c.fileDropManager = m
 }
 

client/internal/engine.go

@@ -40,7 +40,6 @@ import (
 	dnsconfig "github.com/netbirdio/netbird/client/internal/dns/config"
 	"github.com/netbirdio/netbird/client/internal/dnsfwd"
 	"github.com/netbirdio/netbird/client/internal/expose"
-	"github.com/netbirdio/netbird/client/internal/filedrop"
 	"github.com/netbirdio/netbird/client/internal/ingressgw"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
 	"github.com/netbirdio/netbird/client/internal/metrics"
@@ -191,7 +190,7 @@ type EngineServices struct {
 	UpdateManager  *updater.Manager
 	ClientMetrics  *metrics.ClientMetrics
 	MetricsCtx     context.Context
-	FileDrop       *filedrop.Manager
+	FileDrop       fileDropManager
 	// NetMgr gates the reconnection loops on OS-reported network
 	// availability; nil disables gating.
 	NetMgr *netevents.Manager
@@ -254,7 +253,7 @@ type Engine struct {
 
 	sshServer sshServer
 
-	fileDrop        *filedrop.Manager
+	fileDrop        fileDropManager
 	fileDropRunning bool
 	fileDropPort    uint16
 	overlayWait     overlayWaiter //nolint:unused // only read by the iOS overlay wait

client/internal/engine_filedrop.go

@@ -1,3 +1,5 @@
+//go:build !js
+
 package internal
 
 import (

client/internal/engine_filedrop_dial.go

@@ -1,4 +1,4 @@
-//go:build !ios
+//go:build !ios && !js
 
 package internal
 

client/internal/engine_filedrop_js.go

@@ -0,0 +1,14 @@
+//go:build js
+
+package internal
+
+// File drop is not supported on wasm: there is no local filesystem to deliver
+// into and no way to bind a receiver. The engine still calls these on the
+// start, stop and overlay rebind paths, so they exist as no-ops and keep the
+// filedrop package out of the wasm binary.
+
+func (e *Engine) startFileDrop() {}
+
+func (e *Engine) stopFileDrop() {}
+
+func (e *Engine) restartFileDrop() error { return nil }

client/internal/engine_filedrop_type.go

@@ -0,0 +1,7 @@
+//go:build !js
+
+package internal
+
+import "github.com/netbirdio/netbird/client/internal/filedrop"
+
+type fileDropManager = *filedrop.Manager

client/internal/engine_filedrop_type_js.go

@@ -0,0 +1,9 @@
+//go:build js
+
+package internal
+
+// fileDropManager keeps the engine and ConnectClient fields typed on wasm,
+// where file drop is not supported and the manager is always nil. Aliasing a
+// pointer keeps the nil guards and stays out of the filedrop package, so its
+// HTTP server and client never reach the wasm binary.
+type fileDropManager = *struct{}