feat(cli): version subcommand + --version flag; rename functional marker

[phitoduck]

Summary

loseit version + loseit --version

Both print the same payload:

loseit 0.2.0
Release: https://github.com/phitoduck/lose-it/releases/tag/v0.2.0
License: MIT

This project is unaffiliated with Lose It! / FitNow, Inc.
Thank you for using it!

• Release URL uses the v-prefixed tag pushed by the tag-release CI job.
• License (MIT) read from a single constant.
• --version is eager — it short-circuits before any config/auth lookup, so it works on a bare clone with no LOSEIT_* env vars or token.
• loseit --output json version (or toon) emits the same fields as a structured envelope.

The CLI reads the version via importlib.metadata.version("lose-it") so the displayed version always matches the installed dist (which hatchling populates from version.txt). There's a small fallback to reading version.txt directly for python -m lose_it.cli runs against an uninstalled source tree.

requires_auth marker (replaces LOSEIT_RUN_FUNCTIONAL=1)

• New @pytest.mark.requires_auth marker on every test under tests/functional/ that touches the live API.
• tests/conftest.py adds a --run-auth pytest CLI flag and skips requires_auth tests unless the flag is passed.
• All four tests/functional/test_*.py files drop their per-file env-var _gate() autouse fixtures.
• pyproject.toml marker entry, .github/workflows/ci.yml commentary, and the README's contributing + testing sections all updated to reference --run-auth instead of the env var. CI's pytest invocation is unchanged — requires_auth tests just self-skip without the flag.

Tests

New tests/conformance/test_version.py (4 tests, no network, no auth):

• version subcommand prints all required fields in text mode.
• --version global flag prints the same payload.
• --output json version emits the structured envelope.
• --version works with every LOSEIT_* env var unset.

Version bumped 0.1.0 → 0.2.0 (minor — new CLI surface, per AGENTS.md).

Test plan

• uv run pytest --no-cov -q → 165 passed, 5 skipped (requires_auth).
• uv run pytest --run-auth --collect-only → all 170 tests collected.
• uv run ruff check . + uv run ruff format --check . clean.
• uv build produces lose_it-0.2.0.tar.gz + wheel.
• uv run loseit version and uv run loseit --version print correct text.
• uv run loseit --output json version and --output toon version emit structured payloads.
• CI version-check job sees v0.2.0 as unreleased.
• Tag v0.2.0 appears on the repo after merge.