fix: add main/main.go entry point for luxd binary

Restores the missing entry point that .goreleaser.yml, Makefile, and
scripts/build.sh all expect at ./main. Without this file, the release
pipeline fails with 'couldn't find main file: stat main: no such file
or directory'.

The main wires:
  config.BuildFlagSet → config.BuildViper → config.GetNodeConfig
  → log.NewFactoryWithConfig → ulimit.Set
  → node.New(*node.Config, log.Factory, log.Logger)
  → n.Dispatch() with SIGINT/SIGTERM handling
  → exit n.ExitCode()

--version short-circuits to print version.CurrentApp.String() (e.g.
'luxd/1.23.25').

Not using the orphan app/ package (app.New takes nodeconfig.Config which
is a parallel type definition not produced by config.GetNodeConfig). The
app/ package can be migrated separately or removed.

main/main.go

@@ -0,0 +1,101 @@
+// Copyright (C) 2019-2026, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+// luxd — Lux Network node daemon.
+//
+// Entry point for the Lux primary-network node binary. Loads configuration
+// from CLI flags + config files via Viper, constructs a [node.Node], and
+// dispatches the main event loop.
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/luxfi/log"
+	"github.com/luxfi/node/config"
+	"github.com/luxfi/node/node"
+	"github.com/luxfi/node/version"
+	"github.com/luxfi/sys/ulimit"
+)
+
+const Header = `
+▼▼▼▼▼
+ ▼▼▼
+  ▼
+`
+
+func main() {
+	if exitCode := run(os.Args[1:]); exitCode != 0 {
+		os.Exit(exitCode)
+	}
+}
+
+func run(args []string) int {
+	// --version short-circuit
+	for _, a := range args {
+		if a == "--version" || a == "-v" {
+			fmt.Println(version.CurrentApp.String())
+			return 0
+		}
+	}
+
+	fmt.Print(Header)
+
+	// Parse CLI + config file via Viper.
+	fs := config.BuildFlagSet()
+	v, err := config.BuildViper(fs, args)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "luxd: failed to parse config:", err)
+		return 1
+	}
+	cfg, err := config.GetNodeConfig(v)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "luxd: failed to load node config:", err)
+		return 1
+	}
+
+	// Logger.
+	infoLevel, _ := log.ToLevel("info")
+	logFactory := log.NewFactoryWithConfig(log.Config{
+		DisplayLevel: infoLevel,
+		LogLevel:     infoLevel,
+	})
+	logger, err := logFactory.Make("node")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "luxd: failed to construct logger:", err)
+		return 1
+	}
+
+	// Bump file descriptor limit early; node + its plugins open many sockets.
+	if err := ulimit.Set(ulimit.DefaultFDLimit, logger); err != nil {
+		logger.Error("failed to set fd limit", "error", err)
+		return 1
+	}
+
+	// Construct the node.
+	n, err := node.New(&cfg, logFactory, logger)
+	if err != nil {
+		logger.Error("failed to construct node", "error", err)
+		return 1
+	}
+
+	// Run dispatch loop with signal-driven shutdown.
+	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer cancel()
+	go func() {
+		<-ctx.Done()
+		logger.Info("received shutdown signal")
+		n.Shutdown(0)
+	}()
+
+	if err := n.Dispatch(); err != nil && !errors.Is(err, context.Canceled) {
+		logger.Error("dispatch returned error", "error", err)
+		return 1
+	}
+	return n.ExitCode()
+}