Phase 0: project skeleton

- pyproject.toml with uv, deps for runtime + gui + backtest + dev
- ruff/mypy strict config, pre-commit hooks for ruff/mypy/pytest
- src/cerbero_bite/ layout with empty modules ready for Phase 1+
- structlog JSONL logger with daily rotation
- click CLI with placeholder subcommands (status, start, kill-switch,
  gui, replay, config hash, audit verify)
- 6 smoke tests passing, mypy --strict clean, ruff clean

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,23 @@
+"""Shared pytest fixtures for Cerbero Bite tests."""
+
+from __future__ import annotations
+
+from collections.abc import Iterator
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def tmp_data_dir(tmp_path: Path) -> Iterator[Path]:
+    """Isolated data directory with the standard subfolder layout."""
+    data = tmp_path / "data"
+    (data / "log").mkdir(parents=True)
+    (data / "backups").mkdir()
+    yield data
+
+
+@pytest.fixture
+def project_root() -> Path:
+    """Path to the project root (parent of ``src/``)."""
+    return Path(__file__).resolve().parent.parent