feat: dynamic database credentials + docker-compose generation

[dipto0321]

Summary

• Dynamic DB credentials: the wizard now asks for database name / user / password (PostgreSQL; db name only for MongoDB), with --db-name / --db-user / --db-password flags for non-interactive use. Defaults: slug / slug / auto-generated secrets.token_urlsafe(16).
• Real credentials flow into .env; .env.example always gets the change-me-db-password placeholder — the real password never lands in a committed file.
• New docker-compose.yml per project (postgres:16-alpine and/or mongo:7, ports bound to 127.0.0.1, volumes, healthcheck) wired to the same credentials, so docker compose up -d gives a working database on first run.
• Version bumped to 0.3.0.

Bug fixes (from the 2026-07-14 end-to-end review)

1. FastAPI/Flask MongoDB-only projects crashed on import (No module named 'psycopg') — SQL layer now falls back to SQLite.
2. Django: bare manage.py makemigrations detected nothing (missing migrations/__init__.py packages).
3. Django: pytest required a running PostgreSQL — new config/settings/test.py uses SQLite.
4. FastAPI --auth none: alembic revision --autogenerate crashed on a nonexistent auth import.
5. Fresh projects crashed on first boot with no local Postgres — fixed by the compose file + README quickstart step.
6. Success panel showed FastAPI instructions (and cp .env.example .env) for every framework — now framework-aware.

Verification

• 82/82 unit tests pass, ruff clean.
• E2E matrix: 5 generated projects (fastapi/flask/django × postgres, fastapi × mongo-only, fastapi × no-auth) — all install, their test suites pass without PostgreSQL running, makemigrations creates 0001_initial, alembic autogenerate works, docker compose config validates.
• Multi-agent review per task plus a final whole-branch review (verdict: ready to merge).

🤖 Generated with Claude Code

[cocogitto-bot]

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