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

README.md

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+# Habit Tracker API
+
+Self-hosted habit tracking service with a clean, hexagonal architecture.
+
+## Features
+
+- **Multiple habit types**: Boolean (check), Counter, Value
+- **Flexible scheduling**: Daily, Weekly, Monthly with specific days
+- **Carry-over support**: Choose if incomplete habits persist or expire
+- **Full history tracking**: Complete audit trail of all interactions
+- **Charts & Analytics**: Heatmaps, line charts, and statistics
+- **Self-hosted first**: Easy deployment with SQLite or PostgreSQL
+
+## Quick Start
+
+### Using the binary
+
+1. Download the latest release
+2. Copy `.env.example` to `.env` and configure
+3. Run: `./habit-tracker-api`
+
+The API will be available at `http://localhost:8080`
+
+## Development
+
+### Prerequisites
+
+- Go 1.23+
+- SQLite (or PostgreSQL)
+
+### Running locally
+
+```bash
+cp .env.example .env
+go run cmd/api/main.go
+```
+
+## API Documentation
+
+Once running, visit `http://localhost:8080/api/v1/docs` for interactive API documentation.
+
+## Architecture
+
+This project follows hexagonal (ports & adapters) architecture:
+
+- `domain/`: Core business logic and entities
+- `application/`: Use cases (commands & queries)
+- `infrastructure/`: External adapters (database, HTTP, etc.)
+- `shared/`: Common utilities and errors
+
+## License
+
+MIT