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.

.env.example

@@ -0,0 +1,8 @@
+WARPBOX_APP_NAME=warpbox.dev
+WARPBOX_ENV=development
+WARPBOX_ADDR=:8080
+WARPBOX_BASE_URL=http://localhost:8080
+WARPBOX_MAX_UPLOAD_SIZE_MB=2048
+WARPBOX_READ_TIMEOUT=15s
+WARPBOX_WRITE_TIMEOUT=60s
+WARPBOX_IDLE_TIMEOUT=120s