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>

frontend/Dockerfile.prod

@@ -0,0 +1,24 @@
+# syntax=docker/dockerfile:1
+
+FROM node:20-alpine AS build
+
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+COPY . .
+
+ARG VITE_DATA_MODE=local
+ENV VITE_DATA_MODE=${VITE_DATA_MODE}
+
+RUN npm run build
+
+FROM nginx:1.27-alpine AS runtime
+
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /app/dist /usr/share/nginx/html
+
+EXPOSE 80
+
+CMD ["nginx", "-g", "daemon off;"]