M0: scaffold SPA + API monorepo

Backend (Django 6.1 + DRF):
- Token auth with a custom User model (register/login/logout/me)
- Library models (MediaItem, MediaLocation) and REST endpoints
- File list/detail with search, rating filter, sorting, pagination
- Multipart upload with optional rating/tags/notes
- Range-aware media serving (video seeking) and ffmpeg thumbnails
- scan_files management command for the watched folder

Frontend (React 19 + Vite + TypeScript):
- Catppuccin Mocha design tokens from the design docs
- App shell, token persistence, protected routes
- Library grid with filters, file detail with custom data editor
- Upload page with per-file progress via XHR
- Dev proxy to the Django API

README.md

@@ -0,0 +1,38 @@
+# J621
+
+Self-hosted media library and e621 archive manager, rebuilt as a **React SPA + Django REST API**.
+
+## Structure
+
+```
+backend/    Django 6 + DRF API (SQLite in dev, MariaDB in production)
+frontend/   Vite + React + TypeScript SPA
+```
+
+## Development
+
+### Backend
+
+```bash
+cd backend
+source venv/bin/activate
+python manage.py migrate
+python manage.py scan_files            # index the watched folder
+python manage.py runserver
+```
+
+Copy `.env.example` to `.env` and set `WATCHED_FOLDER` before scanning.
+
+### Frontend
+
+```bash
+cd frontend
+npm install
+npm run dev                            # http://localhost:5173, proxies /api to :8000
+```
+
+### Production
+
+Not wired up yet — planned: Nginx serving the SPA build, `/media` and `/library` media
+directly, and proxying `/api` to Waitress/Django. See `frontend/` design docs for the UI
+specification.