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/libs/handlers/static.go

@@ -0,0 +1,31 @@
+package handlers
+
+import (
+	"net/http"
+	"path/filepath"
+	"strings"
+)
+
+func (a *App) Static() http.Handler {
+	fileServer := http.StripPrefix("/static/", http.FileServer(http.Dir(a.cfg.StaticDir)))
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		setStaticCacheHeaders(w, r.URL.Path)
+		fileServer.ServeHTTP(w, r)
+	})
+}
+
+func setStaticCacheHeaders(w http.ResponseWriter, path string) {
+	ext := strings.ToLower(filepath.Ext(path))
+
+	switch ext {
+	case ".avif", ".gif", ".ico", ".jpg", ".jpeg", ".png", ".svg", ".webp",
+		".mp4", ".m4v", ".mov", ".webm", ".mp3", ".ogg",
+		".eot", ".otf", ".ttf", ".woff", ".woff2":
+		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+	case ".css", ".js":
+		w.Header().Set("Cache-Control", "public, max-age=86400")
+	default:
+		w.Header().Set("Cache-Control", "public, max-age=3600")
+	}
+}