chore: replace Docker setup with Nixpacks configuration

- Remove Dockerfile and docker-compose.yml in favor of nixpacks.toml
- Keep backup files (Dockerfile.bak, docker-compose.yml.bak) for reference
- Nixpacks provides a simpler, declarative approach to building and deploying

Dockerfile.bak

@@ -0,0 +1,24 @@
+FROM node:18-alpine
+
+WORKDIR /app
+
+# Install build dependencies for native modules (sqlite3)
+RUN apk add --no-cache python3 make g++
+
+COPY package*.json ./
+
+RUN npm install
+
+COPY . .
+
+# Ensure data directory exists
+RUN mkdir -p data
+
+RUN npm run build
+
+EXPOSE 3000
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
+  CMD wget --no-verbose --tries=1 --spider http://127.0.0.1:3000/health || exit 1
+
+CMD ["npm", "start"]