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.

README.md

@@ -0,0 +1,41 @@
+# Warpbox.dev
+
+This repository contains the Go backend base for `warpbox.dev`, a self-hosted transfer-first file sharing application.
+
+## Run
+
+```bash
+./scripts/run/dev.sh
+```
+
+The default server listens on `:8080`.
+
+Upload size limits are configured in megabytes through `WARPBOX_MAX_UPLOAD_SIZE_MB`.
+Fractions are supported, so `0.5Mb` is 512 KiB and `1.5Mb` is 1536 KiB.
+
+For one-off Go commands, run them from the backend module:
+
+```bash
+cd backend
+go run ./cmd/warpbox
+```
+
+## Layout
+
+- `backend/cmd/warpbox` - main application entry point.
+- `backend/libs/config` - environment-backed configuration.
+- `backend/libs/httpserver` - server construction and route composition.
+- `backend/libs/handlers` - HTTP handlers for pages, API, health, static files.
+- `backend/libs/middleware` - request logging, recovery, security headers, gzip, request IDs.
+- `backend/libs/services` - business logic boundaries, starting with upload limits.
+- `backend/libs/helpers` - small reusable helpers.
+- `backend/libs/web` - Go template renderer.
+- `backend/templates` - server-rendered Go templates.
+- `backend/static/css`, `backend/static/js`, `backend/static/img`, `backend/static/fonts` - public assets served from `/static/`.
+- `scripts/run/dev.sh` - local development runner.
+- `scripts/env/dev.env.example` - tracked development environment template.
+- `scripts/env/dev.env` - local development environment, ignored by git.
+
+## Static Asset Policy
+
+The static handler sets long-lived immutable caching for images, video, audio, and fonts, shorter caching for CSS/JS, and gzip compression for compressible responses. Upload storage is intentionally only a placeholder at this stage.