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.

.env.example

@@ -1,9 +1,16 @@
 CLIENT_ID=VOTRE_BOT_CLIENT_ID
 CLIENT_SECRET=VOTRE_BOT_CLIENT_SECRET
 REDIRECT_URI=https://lazybot.arthurp.fr/auth/discord/callback
+NODE_ENV=development
 PORT=3000
 BOT_TOKEN=VOTRE_BOT_TOKEN
 SESSION_SECRET=UN_SECRET_LONG_ET_UNIQUE
-DB_PATH=database.sqlite
+POSTGRES_HOST=db
+POSTGRES_PORT=5432
+POSTGRES_DB=lazybot
+POSTGRES_USER=lazybot
+POSTGRES_PASSWORD=change_me
+POSTGRES_DATA_PATH=./data/postgres
+DATABASE_URL=postgresql://lazybot:change_me@db:5432/lazybot
 OWNER=VOTRE_ID_UTILISATEUR
 URL=https://lazybot.arthurp.fr