Initial project setup with MIT license

- Add MIT License (Copyright 2025 David Folch Agulles)
- Add README with project description
- Add .gitignore for Go project
- Add .env.example for configuration
- Initialize Go module

.env.example

@@ -0,0 +1,13 @@
+DB_TYPE=sqlite
+DB_PATH=./data/habits.db
+
+PORT=8080
+HOST=0.0.0.0
+
+JWT_SECRET=change-me-in-production
+JWT_EXPIRY=24h
+REFRESH_TOKEN_EXPIRY=168h
+
+CORS_ORIGINS=http://localhost:3000
+
+DEFAULT_TIMEZONE=UTC