WP-0001-T014: minimal HTTP app and CLI

src/artifactstore/app.py (new): composition root. build_registry(settings)
wires AsyncEngine + LocalBackend + InProcessDataPlane + RegistryViewWriter
into a Registry. Used by both the HTTP app and the CLI.

src/artifactstore/registry/__init__.py: adds db_health() (SELECT 1 probe),
backend_health() (pass-through to dataplane), and dispose() (engine
shutdown) helpers so the HTTP /health endpoint and CLI commands can talk
to the registry without reaching for private state.

src/artifactstore/api/http/__init__.py:
- create_app(settings=None) factory; lifespan owns the registry instance
  and disposes it on shutdown.
- GET / returns the scaffold banner.
- GET /health reports overall status + db {healthy, detail} + backend
  {backend_id, healthy, detail, free_bytes, total_bytes}. Uses
  FastAPI Depends() with a request->state.registry helper rather than
  reaching app.state directly.
- Module-level `app = create_app()` so `uvicorn artifactstore.api.http:app`
  keeps working.

src/artifactstore/cli/__init__.py:
- migrate: `alembic upgrade head` via the alembic command API.
- replay: drops + rebuilds materialised views from the event log; prints
  the highest applied sequence.
- health: prints the same payload as the HTTP /health endpoint, as JSON.
- version unchanged.

Tests:
- tests/integration/test_http_health.py (TestClient-based): /
  scaffold banner; /health reports ok with db.healthy + backend.healthy
  + free_bytes populated.
- tests/integration/test_cli_commands.py (typer CliRunner): version
  prints; migrate creates the schema (events + retention_classes +
  alembic_version); replay against an empty log exits ok with
  "replayed up to sequence 0"; health prints a status=ok JSON payload.

Gates: ruff clean, mypy --strict clean on 48 files, 83 tests pass.

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

src/artifactstore/app.py

@@ -0,0 +1,27 @@
+"""Composition root: build the runtime registry from settings.
+
+The HTTP server, the CLI, and any future host all instantiate the
+:class:`Registry` through :func:`build_registry`. Wiring lives here so the
+control-plane consumers stay thin (per ADR-0004).
+"""
+
+from __future__ import annotations
+
+from artifactstore.config import Settings, get_settings
+from artifactstore.dataplane import InProcessDataPlane
+from artifactstore.db.engine import create_engine
+from artifactstore.events import RegistryViewWriter
+from artifactstore.registry import Registry
+from artifactstore.storage import LocalBackend
+
+__all__ = ["build_registry"]
+
+
+def build_registry(settings: Settings | None = None) -> Registry:
+    """Wire engine, local FS backend, in-process data plane, and registry."""
+    effective = settings or get_settings()
+    engine = create_engine(effective)
+    backend = LocalBackend(effective.storage_local_root, backend_id="local")
+    dataplane = InProcessDataPlane(backend)
+    view_writer = RegistryViewWriter()
+    return Registry(engine, dataplane, view_writer)