Add local-first SPA architecture and containerized production deploy.

Move data access to use-cases and IndexedDB repositories with optional
remote fallback, changelog/sync ports, and encrypted local backup.
Add production Docker Compose (nginx frontend + optional backend) and
Apache host proxy configuration for deployment.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/Dockerfile.prod

@@ -0,0 +1,18 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+
+ENV PYTHONDONTWRITEBYTECODE=1
+ENV PYTHONUNBUFFERED=1
+ENV DJANGO_SETTINGS_MODULE=config.settings
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt gunicorn
+
+COPY . .
+
+RUN mkdir -p /app/data
+
+EXPOSE 8000
+
+CMD ["sh", "-c", "python manage.py migrate --noinput && gunicorn config.wsgi:application --bind 0.0.0.0:8000 --workers 2 --timeout 120"]