feat: add consumer configuration policy

[codeforester]

Summary

• Add a validated Northstar-owned configuration model and explicit profile adapter.
• Demonstrate default and commerce-specific policy paths with provenance output.
• Keep Base-CLI lifecycle settings separate from consumer configuration.

Validation

• ./tests/validate.sh
• UV_CACHE_DIR=/private/tmp/base-cli-demo-issue3-uv uv run --extra dev pytest -q (8 passed)
• UV_CACHE_DIR=/private/tmp/base-cli-demo-issue3-uv uv run --with ruff ruff check src tests
• UV_CACHE_DIR=/private/tmp/base-cli-demo-issue3-uv uv run --with ruff ruff format --check src tests

Fixes #3