refactor: migrate from SQLite to PostgreSQL for session management and data storage

- Updated package dependencies to replace SQLite with PostgreSQL.
- Modified privacy policy to reflect the change in database technology.
- Adjusted session management in server.js to use connect-pg-simple.
- Enhanced docker-compose.yml to include PostgreSQL service with health checks.
- Added Dockerfile for multi-stage builds for development and production environments.
- Introduced .dockerignore to exclude unnecessary files from the Docker context.

.gitignore

@@ -74,6 +74,9 @@ web_modules/
 .env.*
 !.env.example
 
+# Docker volumes
+data/postgres/
+
 # parcel-bundler cache (https://parceljs.org/)
 .cache
 .parcel-cache