feat: initialize warpbox.dev project structure and backend

Initialize the repository with the core Go backend architecture and a frontend mockup for warpbox.dev, a self-hosted file-sharing application.

- Set up Go backend modules for configuration, HTTP server, middleware, handlers, and templates.
- Add local development scripts, environment templates, and basic project configuration.
- Include a React-based frontend mockup under the docs directory.

backend/cmd/warpbox/main.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"warpbox.dev/backend/libs/config"
+	"warpbox.dev/backend/libs/httpserver"
+)
+
+func main() {
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+		Level: slog.LevelInfo,
+	}))
+
+	cfg, err := config.Load()
+	if err != nil {
+		logger.Error("failed to load config", "error", err)
+		os.Exit(1)
+	}
+
+	server, err := httpserver.New(cfg, logger)
+	if err != nil {
+		logger.Error("failed to create server", "error", err)
+		os.Exit(1)
+	}
+
+	errs := make(chan error, 1)
+	go func() {
+		logger.Info("warpbox server starting", "addr", cfg.Addr, "env", cfg.Environment)
+		errs <- server.ListenAndServe()
+	}()
+
+	shutdown := make(chan os.Signal, 1)
+	signal.Notify(shutdown, syscall.SIGINT, syscall.SIGTERM)
+
+	select {
+	case err := <-errs:
+		if err != nil && !errors.Is(err, http.ErrServerClosed) {
+			logger.Error("server stopped unexpectedly", "error", err)
+			os.Exit(1)
+		}
+	case sig := <-shutdown:
+		logger.Info("shutdown signal received", "signal", sig.String())
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+
+		if err := server.Shutdown(ctx); err != nil {
+			logger.Error("graceful shutdown failed", "error", err)
+			os.Exit(1)
+		}
+		logger.Info("server stopped")
+	}
+}