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/middleware/recoverer.go

@@ -0,0 +1,26 @@
+package middleware
+
+import (
+	"log/slog"
+	"net/http"
+	"runtime/debug"
+)
+
+func Recoverer(logger *slog.Logger) Middleware {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			defer func() {
+				if recovered := recover(); recovered != nil {
+					logger.Error("panic recovered",
+						"error", recovered,
+						"stack", string(debug.Stack()),
+						"request_id", RequestIDFromContext(r.Context()),
+					)
+					http.Error(w, "internal server error", http.StatusInternalServerError)
+				}
+			}()
+
+			next.ServeHTTP(w, r)
+		})
+	}
+}