[EPIC] v1.3.0 Modern API Starter

[bnbong]

Summary

Track the v1.3.0 release theme: make FastAPI-fastkit opinionated around a modern default API starter instead of only expanding template count.

Goals

• Add a new recommended starter template based on domain-oriented structure
• Add architecture presets to fastkit init --interactive
• Modernize template standards to be pyproject.toml-first
• Improve docs so users can choose the right starter confidently
• Strengthen automated coverage for new template and preset behavior

Non-Goals

• Full-stack frontend template work
• Microservice/serverless/GraphQL/ML templates
• Completing all translations in this release

Child Issues

• Add pyproject-first template contract
• Add fastapi-domain-starter template
• Add architecture preset selection
• Support preset-aware generation
• Add E2E and regression coverage
• Add starter selection docs
• Add domain starter tutorial
• Add translation completeness notice
• Fix Korean docs indexing issue
• Prepare release checklist

Release Gates

• All child issues closed
• uv run pytest tests/ passes
• uv run mkdocs build passes
• New template passes template inspection
• Interactive preset flow is covered by tests
• Release notes and changelog updated

Notes

This epic is for tracking only. Do not implement the entire epic in a single PR.