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

AGENTS.md

@@ -0,0 +1,7 @@
+Use the venv on backend/venv/
+
+DO NOT mess with the system's python
+
+For Frontend work:
+
+read both Frontend Design related Markdown files on the frontend/ folder