feat: add the flagship base-cli consumer

[codeforester]

Summary

Implements the first runnable consumer application for base-cli.

• Adds the installable Northstar CLI with nested status and release commands.
• Uses deterministic local service fixtures and the public base_cli facade.
• Demonstrates lifecycle environment selection, output rendering, dry-run mode, and the JSON envelope.
• Adds a five-minute quickstart, package metadata, consumer tests, and CI execution.

Validation

• ./tests/validate.sh
• uv run --extra dev pytest -q
• uv run --with ruff ruff check src tests
• uv run --with ruff ruff format --check src tests
• uv build --wheel
• Non-editable wheel smoke for status, JSON envelope, and dry-run reconciliation

Scope boundary

This issue intentionally does not add Base dependencies, cloud services, Docker, multi-language consumers, or ecosystem Catalog behavior.

Fixes #1