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_test.go

@@ -0,0 +1,26 @@
+package handlers
+
+import (
+	"net/http/httptest"
+	"testing"
+)
+
+func TestSetStaticCacheHeaders(t *testing.T) {
+	tests := map[string]string{
+		"/static/css/app.css":       "public, max-age=86400",
+		"/static/js/app.js":         "public, max-age=86400",
+		"/static/img/preview.webp":  "public, max-age=31536000, immutable",
+		"/static/fonts/ui.woff2":    "public, max-age=31536000, immutable",
+		"/static/videos/intro.mp4":  "public, max-age=31536000, immutable",
+		"/static/uploads/file.data": "public, max-age=3600",
+	}
+
+	for path, want := range tests {
+		response := httptest.NewRecorder()
+		setStaticCacheHeaders(response, path)
+
+		if got := response.Header().Get("Cache-Control"); got != want {
+			t.Fatalf("Cache-Control for %s = %q, want %q", path, got, want)
+		}
+	}
+}