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

docker-compose.yml.bak

@@ -0,0 +1,17 @@
+version: '3.8'
+services:
+  web:
+    build: .
+    ports:
+      - "3000:3000"
+    volumes:
+      - ./data:/app/data
+    environment:
+      - PORT=3000
+      - NODE_ENV=production
+    healthcheck:
+      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://127.0.0.1:3000/health"]
+      interval: 30s
+      timeout: 3s
+      retries: 3
+      start_period: 10s