chore: add .env.example file with environment variable templates

.env.example

@@ -0,0 +1,36 @@
+# Global
+NODE_ENV=development
+
+# Backend
+BACKEND_PORT=3001
+
+# Frontend
+FRONTEND_PORT=3000
+
+# Database (PostgreSQL)
+POSTGRES_HOST=localhost
+POSTGRES_PORT=5432
+POSTGRES_DB=memegoat
+POSTGRES_USER=app
+POSTGRES_PASSWORD=app
+
+# Storage (S3/MinIO) - À configurer lors de l'implémentation
+# S3_ENDPOINT=localhost
+# S3_PORT=9000
+# S3_ACCESS_KEY=
+# S3_SECRET_KEY=
+# S3_BUCKET=memegoat
+
+# Security (PGP & Auth) - À configurer lors de l'implémentation
+# PGP_PASSPHRASE=
+JWT_SECRET=super-secret-key-change-me-in-production
+ENCRYPTION_KEY=another-super-secret-key-32-chars
+
+# Mail
+MAIL_HOST=localhost
+MAIL_PORT=1025
+MAIL_SECURE=false
+MAIL_USER=user
+MAIL_PASS=password
+MAIL_FROM=noreply@memegoat.fr
+DOMAIN_NAME=memegoat.fr