⚙️ FEATURE-#107: Rewrite dotflow init with interactive cookiecutter template

[FernandoCelmer]

Description

• pyproject.toml: Added cookiecutter as dependency
• dotflow/cli/commands/init.py: Rewritten to use cookiecutter with remote template from dotflow-io/template
• dotflow/cli/setup.py: Simplified init command setup (no args needed, cookiecutter handles prompts)
• docs/nav/learn/cli/init.md: New documentation page
• mkdocs.yml: Added init to CLI nav

Motivation and Context

dotflow init now scaffolds a project interactively, prompting for project name and storage backend. Uses cookiecutter with a remote template repo (dotflow-io/template) supporting default, file, S3, and GCS storage options.

Closes #107

Types of changes

• New feature (change which adds functionality)
• Documentation

Checklist

• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• I have updated the CHANGELOG
• I have updated the documentation accordingly