fix(ffi): Singcast 懒初始化 svc 字段，兼容 gomobile 零值构造器

gomobile 生成的 Java Singcast() 构造器创建零值 Go 结构体，
导致 svc 字段为 nil，Init/SetOnEvent 等方法调用时崩溃。

添加 service() 方法做懒初始化，所有方法通过它访问 svc。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: mapleafgo

ffi/api.go

@@ -38,37 +38,45 @@ func New() *Singcast {
 	return &Singcast{svc: core.NewService()}
 }
 
+// service returns the core.Service, initializing lazily for gomobile zero-value compatibility.
+func (s *Singcast) service() *core.Service {
+	if s.svc == nil {
+		s.svc = core.NewService()
+	}
+	return s.svc
+}
+
 // Init initializes the core runtime.
 // optionsJSON: {"home_dir":"/path","log_max_lines":500,"debug":false,"fix_android_stack":false}
 func (s *Singcast) Init(optionsJSON string) error {
-	return s.svc.Init(optionsJSON)
+	return s.service().Init(optionsJSON)
 }
 
 // StartWithContent starts or restarts the service with raw YAML or JSON config.
 func (s *Singcast) StartWithContent(content, ruleSetProxy string) error {
-	return s.svc.StartWithContent(content, ruleSetProxy)
+	return s.service().StartWithContent(content, ruleSetProxy)
 }
 
 // Stop stops the running service. Safe to call multiple times.
 func (s *Singcast) Stop() error {
-	return s.svc.Stop()
+	return s.service().Stop()
 }
 
 // Destroy releases all resources. The instance cannot be reused.
 func (s *Singcast) Destroy() {
-	s.svc.Destroy()
+	s.service().Destroy()
 }
 
 // --- Platform IO ---
 
 // SetTunFd stores a TUN file descriptor for mobile platforms.
 func (s *Singcast) SetTunFd(fd int32) {
-	s.svc.PlatformIO().SetTunFd(fd)
+	s.service().PlatformIO().SetTunFd(fd)
 }
 
 // SetSocketProtector registers a socket protector for VPN bypass.
 func (s *Singcast) SetSocketProtector(p SocketProtector) {
-	s.svc.PlatformIO().SetSocketProtector(func(fd int32) bool {
+	s.service().PlatformIO().SetSocketProtector(func(fd int32) bool {
 		if p != nil {
 			return p.Protect(fd)
 		}
@@ -78,64 +86,64 @@ func (s *Singcast) SetSocketProtector(p SocketProtector) {
 
 // SetInterfacesJSON provides network interface data from the mobile platform.
 func (s *Singcast) SetInterfacesJSON(json string) {
-	s.svc.PlatformIO().SetInterfacesJSON(json)
+	s.service().PlatformIO().SetInterfacesJSON(json)
 }
 
 // UpdateDefaultInterface reports the current default network interface.
 func (s *Singcast) UpdateDefaultInterface(name string, index int64, expensive bool) {
-	s.svc.PlatformIO().UpdateDefaultInterface(name, index, expensive)
+	s.service().PlatformIO().UpdateDefaultInterface(name, index, expensive)
 }
 
 // SetIncludeAllNetworks sets whether the VPN configuration uses includeAllNetworks (iOS).
 func (s *Singcast) SetIncludeAllNetworks(v bool) {
-	s.svc.PlatformIO().SetIncludeAllNetworks(v)
+	s.service().PlatformIO().SetIncludeAllNetworks(v)
 }
 
 // SetWIFIState reports the current WiFi SSID and BSSID from the mobile platform.
 func (s *Singcast) SetWIFIState(ssid, bssid string) {
-	s.svc.PlatformIO().SetWIFIState(ssid, bssid)
+	s.service().PlatformIO().SetWIFIState(ssid, bssid)
 }
 
 // QueryTunOptions returns TUN configuration as JSON for mobile consumers.
 // Call after the service has started (OpenTun has been invoked by sing-box).
 func (s *Singcast) QueryTunOptions() string {
-	return s.svc.PlatformIO().QueryTunOptions()
+	return s.service().PlatformIO().QueryTunOptions()
 }
 
 // --- Logging ---
 
 // SetLogLevel sets the minimum log level (2=Error, 3=Warn, 4=Info, 5=Debug, 6=Trace).
-func (s *Singcast) SetLogLevel(level int32) { s.svc.SetLogLevel(level) }
+func (s *Singcast) SetLogLevel(level int32) { s.service().SetLogLevel(level) }
 
 // SetError pushes an error message to connected clients.
-func (s *Singcast) SetError(message string) { s.svc.SetError(message) }
+func (s *Singcast) SetError(message string) { s.service().SetError(message) }
 
 // --- Pause / Wake / Network ---
 
 // Pause suspends network activity. On iOS, auto-wakes after 1 minute.
-func (s *Singcast) Pause() { s.svc.Pause() }
+func (s *Singcast) Pause() { s.service().Pause() }
 
 // Wake resumes network activity after Pause.
-func (s *Singcast) Wake() { s.svc.Wake() }
+func (s *Singcast) Wake() { s.service().Wake() }
 
 // ResetNetwork resets all connections, DNS cache, and forces outbounds to reconnect.
-func (s *Singcast) ResetNetwork() { s.svc.ResetNetwork() }
+func (s *Singcast) ResetNetwork() { s.service().ResetNetwork() }
 
 // --- Config ---
 
 // ReloadConfig reloads the service with new configuration.
 func (s *Singcast) ReloadConfig(content, ruleSetProxy string) error {
-	return s.svc.ReloadConfig(content, ruleSetProxy)
+	return s.service().ReloadConfig(content, ruleSetProxy)
 }
 
 // ReloadTUN restarts the TUN interface without changing configuration.
-func (s *Singcast) ReloadTUN() error { return s.svc.ReloadTUN() }
+func (s *Singcast) ReloadTUN() error { return s.service().ReloadTUN() }
 
 // SetOverridePackages updates the include/exclude package lists for VPN split tunneling.
 // The service restarts with the current config and new package overrides.
 // Pass empty string to clear all overrides.
 func (s *Singcast) SetOverridePackages(overrideJSON string) error {
-	return s.svc.SetOverridePackages(overrideJSON)
+	return s.service().SetOverridePackages(overrideJSON)
 }
 
 // CheckConfig validates a config string (Clash YAML or sing-box JSON).
@@ -145,25 +153,25 @@ func (s *Singcast) CheckConfig(content string) error { return core.CheckConfig(c
 
 // SelectProxy selects a proxy in the given group.
 func (s *Singcast) SelectProxy(group, tag string) error {
-	return s.svc.SelectOutbound(group, tag)
+	return s.service().SelectOutbound(group, tag)
 }
 
 // TestDelay runs a URL test for the given outbound tag.
-func (s *Singcast) TestDelay(name string) error { return s.svc.URLTest(name) }
+func (s *Singcast) TestDelay(name string) error { return s.service().URLTest(name) }
 
 // SetMode sets the clash routing mode (rule, global, or direct).
-func (s *Singcast) SetMode(mode string) error { return s.svc.SetClashMode(mode) }
+func (s *Singcast) SetMode(mode string) error { return s.service().SetClashMode(mode) }
 
 // SetGroupExpand sets the UI expand state for a proxy group.
 func (s *Singcast) SetGroupExpand(group string, expand bool) error {
-	return s.svc.SetGroupExpand(group, expand)
+	return s.service().SetGroupExpand(group, expand)
 }
 
 // --- Queries ---
 
 // QueryProxies returns cached proxy groups as JSON.
 func (s *Singcast) QueryProxies() string {
-	h := s.svc.Handler()
+	h := s.service().Handler()
 	if h == nil {
 		return "[]"
 	}
@@ -172,7 +180,7 @@ func (s *Singcast) QueryProxies() string {
 
 // QueryTraffic returns cached traffic stats as JSON.
 func (s *Singcast) QueryTraffic() string {
-	h := s.svc.Handler()
+	h := s.service().Handler()
 	if h == nil {
 		return "{}"
 	}
@@ -182,49 +190,49 @@ func (s *Singcast) QueryTraffic() string {
 // QueryLogs returns combined sing-box and core internal logs as JSON.
 // If clear is true, the log buffer is cleared after querying.
 func (s *Singcast) QueryLogs(clear bool) string {
-	result := s.svc.QueryLogs()
+	result := s.service().QueryLogs()
 	if clear {
-		_ = s.svc.ClearLogs()
+		_ = s.service().ClearLogs()
 	}
 	return result
 }
 
 // QueryConnections returns cached connections as JSON.
 func (s *Singcast) QueryConnections() string {
-	h := s.svc.Handler()
+	h := s.service().Handler()
 	if h == nil {
 		return "[]"
 	}
 	return h.GetCachedConnectionsJSON()
 }
 
 // CloseConnection closes a connection by ID.
-func (s *Singcast) CloseConnection(id string) error { return s.svc.CloseConnection(id) }
+func (s *Singcast) CloseConnection(id string) error { return s.service().CloseConnection(id) }
 
 // CloseAllConnections closes all active connections.
-func (s *Singcast) CloseAllConnections() error { return s.svc.CloseConnections() }
+func (s *Singcast) CloseAllConnections() error { return s.service().CloseConnections() }
 
 // --- Platform Queries ---
 
 // NeedWIFIState reports whether the current config requires WIFI state monitoring.
-func (s *Singcast) NeedWIFIState() bool { return s.svc.NeedWIFIState() }
+func (s *Singcast) NeedWIFIState() bool { return s.service().NeedWIFIState() }
 
 // NeedFindProcess reports whether the current config requires process finding.
-func (s *Singcast) NeedFindProcess() bool { return s.svc.NeedFindProcess() }
+func (s *Singcast) NeedFindProcess() bool { return s.service().NeedFindProcess() }
 
 // UpdateWIFIState triggers the platform to report current WIFI state.
-func (s *Singcast) UpdateWIFIState() { s.svc.UpdateWIFIState() }
+func (s *Singcast) UpdateWIFIState() { s.service().UpdateWIFIState() }
 
 // WriteMessage writes a log message to the core at the given level.
 func (s *Singcast) WriteMessage(level int32, message string) {
-	s.svc.WriteMessage(level, message)
+	s.service().WriteMessage(level, message)
 }
 
 // FlushSystemDNS attempts to flush the system DNS cache.
-func (s *Singcast) FlushSystemDNS() { s.svc.FlushSystemDNS() }
+func (s *Singcast) FlushSystemDNS() { s.service().FlushSystemDNS() }
 
 // QueryMemoryStats returns current Go runtime memory statistics as JSON.
-func (s *Singcast) QueryMemoryStats() string { return s.svc.QueryMemoryStats() }
+func (s *Singcast) QueryMemoryStats() string { return s.service().QueryMemoryStats() }
 
 // --- Memory ---
 
@@ -241,7 +249,7 @@ func (s *Singcast) Version() string { return core.VersionJSON() }
 
 // SetOnEvent registers an event handler. Call after Init.
 func (s *Singcast) SetOnEvent(handler EventHandler) {
-	s.svc.SetOnEvent(func(eventType int32, jsonPayload string) {
+	s.service().SetOnEvent(func(eventType int32, jsonPayload string) {
 		if handler != nil {
 			handler.OnEvent(eventType, jsonPayload)
 		}