WP-0001-T001: service scaffold (Python, FastAPI, uv, ruff, mypy, pytest)

Lands the smallest credible foundation per ADR-0005:

- pyproject.toml: hatchling build, runtime deps (FastAPI, uvicorn, SQLAlchemy 2.0,
  asyncpg, aiosqlite, alembic, blake3, cbor2, typer, structlog, pydantic,
  pydantic-settings); dev deps (pytest, pytest-asyncio, httpx, hypothesis, ruff,
  mypy); ruff + mypy --strict + pytest configured.
- uv.lock committed.
- Makefile thin shims: install / dev / test / lint / format / type / migrate / clean.
- src/artifactstore/ package skeleton with placeholder __init__.py per concern:
  identity, manifest, events, retention, audit, storage, dataplane, registry,
  api/http (minimal FastAPI app, GET / scaffold banner), cli (typer app with
  version subcommand), config (pydantic-settings).
- tests/{unit,integration}/conftest.py present; unit smoke tests assert package
  imports, HTTP root route, CLI version round-trip, settings defaults.
- .env.example documents ARTIFACTSTORE_DATABASE_URL,
  ARTIFACTSTORE_STORAGE_LOCAL_ROOT, ARTIFACTSTORE_LOG_LEVEL.
- README updated with install / dev / test instructions.
- .gitignore: claude local state, local runtime data (var/, sqlite db).

make lint && make type && make test pass on a clean checkout (4 tests, 20
source files type-clean under mypy --strict).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/artifactstore/config.py

@@ -0,0 +1,30 @@
+"""Application configuration loaded from environment variables.
+
+All settings are read from environment variables prefixed with
+``ARTIFACTSTORE_``. A ``.env`` file at the repository root is honoured for
+local development; see ``.env.example``.
+"""
+
+from __future__ import annotations
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    """Top-level service configuration."""
+
+    model_config = SettingsConfigDict(
+        env_prefix="ARTIFACTSTORE_",
+        env_file=".env",
+        env_file_encoding="utf-8",
+        extra="ignore",
+    )
+
+    database_url: str = "sqlite+aiosqlite:///./var/artifactstore.db"
+    storage_local_root: str = "./var/storage"
+    log_level: str = "INFO"
+
+
+def get_settings() -> Settings:
+    """Return a freshly-loaded :class:`Settings` instance."""
+    return Settings()