feat: add Dockerfile and .dockerignore, refactor backend to use DATA_DIR for database and uploads

Now able to use docker image

Dockerfile

@@ -0,0 +1,26 @@
+# Build frontend
+FROM node:24-alpine AS frontend
+WORKDIR /app/frontend
+COPY frontend/package*.json ./
+RUN npm install
+COPY frontend ./
+RUN npm run build
+
+# Build backend
+FROM node:24-alpine AS backend
+WORKDIR /app
+COPY backend/package*.json ./backend/
+COPY backend/ ./backend/
+RUN cd backend && npm install
+
+RUN mkdir -p /data/uploads && chmod -R 777 /data
+
+# Copy built frontend into backend
+COPY --from=frontend /app/frontend/dist ./frontend/dist
+
+WORKDIR /app/backend
+EXPOSE 3000
+
+ENV DATA_DIR=/data
+
+CMD ["node", "index.js"]