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

backend/apps/accounts/serializers.py

@@ -0,0 +1,22 @@
+from django.contrib.auth.password_validation import validate_password
+from rest_framework import serializers
+
+from .models import User
+
+
+class UserSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = User
+        fields = ["id", "username", "email", "is_staff", "date_joined"]
+        read_only_fields = fields
+
+
+class RegisterSerializer(serializers.ModelSerializer):
+    password = serializers.CharField(write_only=True, validators=[validate_password])
+
+    class Meta:
+        model = User
+        fields = ["username", "email", "password"]
+
+    def create(self, validated_data):
+        return User.objects.create_user(**validated_data)