Create tooling/db/common.py with resolve_db_path(), load_config(),
get_connection(), and ensure_venv(). Update ticket, sprint,
sqlite_connector.py, and decisions_sync.py to import from common
instead of duplicating. Fixes pre-existing NameError in
decisions_sync.py (missing import os). Add pyproject.toml with
ruff config (ruff==0.15.9, CVE-clean) and dev dependencies.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
