P3-A: Add account_id to audit_logs model + migration (backfill via user_id →
users.account_id). log_audit() gains optional account_id param with fallback
SELECT to avoid churn across 40 call sites.
P3-B: Add account_id to tree_shares model + migration (backfill via created_by
→ users.account_id). TreeShare constructor updated in trees.py.
P3-C: Enable RLS on 6 remaining tables: step_ratings, step_usage_log,
target_lists, session_shares, audit_logs, tree_shares.
P3-D: Drop team_id from target_lists — endpoint, schema, and model now use
account_id as the sole isolation key.
P3-E: Append Phase 3 RLS isolation tests for all 6 tables.
test_target_lists.py: fix cross-account test to use Account model (not Team)
and set account_id on new User.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>