refactor(edge): unify dynamic IP detection and prioritize IPv4 reporting

- Align agent, relay, and flared to dynamically resolve IP during heartbeat using the nodeip package (when not manually configured).
- Update GeoIP outbound IP strategy to prefer IPv4 HTTP client lookup using tcp4 dialer and fall back to dual-stack tcp.
- Optimize agent profile fingerprinting to exclude dynamic UptimeSeconds and ReportedAtUnix fields, preventing redundant updates.
- Refactor unit tests to prevent outbound network queries during tests.

internal/apps/relay/config/config.go

@@ -35,6 +35,7 @@ type Config struct {
 	HeartbeatInterval MillisecondDuration `json:"heartbeat_interval"`
 	RequestTimeout    MillisecondDuration `json:"request_timeout"`
 	configPath        string
+	NodeIPConfigured  bool
 }
 
 // Load reads configuration from path, applying environment overrides and defaults.
@@ -54,6 +55,7 @@ func Load(path string) (*Config, error) {
 	}
 	cfg.configPath = path
 	applyEnvOverrides(cfg)
+	cfg.NodeIPConfigured = cfg.NodeIP != ""
 	applyDefaults(cfg, filepath.Dir(path))
 	if err = validate(cfg); err != nil {
 		return nil, err

internal/apps/relay/heartbeat/service.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 
 	edgeheartbeat "github.com/Rain-kl/Wavelet/internal/apps/edge/heartbeat"
+	"github.com/Rain-kl/Wavelet/internal/apps/edge/nodeip"
 	"github.com/Rain-kl/Wavelet/internal/apps/relay/config"
 	"github.com/Rain-kl/Wavelet/internal/apps/relay/frps"
 	"github.com/Rain-kl/Wavelet/internal/apps/relay/httpclient"
@@ -46,6 +47,12 @@ func (s *Service) doHeartbeat(ctx context.Context) {
 	slog.Debug("sending heartbeat")
 
 	runtimeStatus := s.frpsManager.GetRuntimeStatus()
+
+	ip := s.config.NodeIP
+	if !s.config.NodeIPConfigured {
+		ip = nodeip.DetectWithContext(ctx)
+	}
+
 	payload := service.RelayHeartbeatPayload{
 		Version:         config.Version,
 		ExtVersion:      s.frpsManager.GetVersion(ctx),
@@ -55,7 +62,7 @@ func (s *Service) doHeartbeat(ctx context.Context) {
 		FrpsClientCount: runtimeStatus.ClientCount,
 		FrpsProxies:     runtimeStatus.Proxies,
 		Name:            s.config.NodeName,
-		IP:              s.config.NodeIP,
+		IP:              ip,
 		Profile:         observability.BuildProfile(s.config, s.stateStore),
 		Snapshot:        observability.BuildSnapshot(s.config, s.stateStore),
 		HealthEvents:    observability.BuildHealthEvents(runtimeStatus),