feat: tenant isolation Phase 3 — audit_logs, tree_shares, remaining RLS

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>

backend/app/api/endpoints/target_lists.py

@@ -18,12 +18,10 @@ async def list_target_lists(
     current_user: Annotated[User, Depends(get_current_active_user)],
     db: Annotated[AsyncSession, Depends(get_db)],
 ):
-    """List all target lists for the current user's team."""
-    if not current_user.team_id:
-        return []
+    """List all target lists for the current user's account."""
     result = await db.execute(
         select(TargetList)
-        .where(TargetList.team_id == current_user.team_id)
+        .where(TargetList.account_id == current_user.account_id)
         .order_by(TargetList.name)
     )
     return result.scalars().all()
@@ -36,11 +34,9 @@ async def create_target_list(
     db: Annotated[AsyncSession, Depends(get_db)],
     _: None = Depends(require_engineer_or_admin),
 ):
-    """Create a new target list for the current team."""
-    if not current_user.team_id:
-        raise HTTPException(status_code=400, detail="User must belong to a team")
+    """Create a new target list for the current account."""
     target_list = TargetList(
-        team_id=current_user.team_id,
+        account_id=current_user.account_id,
         created_by=current_user.id,
         name=data.name,
         description=data.description,
@@ -61,7 +57,7 @@ async def get_target_list(
     result = await db.execute(
         select(TargetList).where(
             TargetList.id == list_id,
-            TargetList.team_id == current_user.team_id,
+            TargetList.account_id == current_user.account_id,
         )
     )
     target_list = result.scalar_one_or_none()
@@ -81,7 +77,7 @@ async def update_target_list(
     result = await db.execute(
         select(TargetList).where(
             TargetList.id == list_id,
-            TargetList.team_id == current_user.team_id,
+            TargetList.account_id == current_user.account_id,
         )
     )
     target_list = result.scalar_one_or_none()
@@ -91,7 +87,7 @@ async def update_target_list(
     if "name" in update_fields and data.name is not None:
         target_list.name = data.name
     if "description" in update_fields:
-        target_list.description = data.description  # allow setting to None
+        target_list.description = data.description
     if "targets" in update_fields and data.targets is not None:
         target_list.targets = [t.model_dump() for t in data.targets]
     await db.commit()
@@ -109,7 +105,7 @@ async def delete_target_list(
     result = await db.execute(
         select(TargetList).where(
             TargetList.id == list_id,
-            TargetList.team_id == current_user.team_id,
+            TargetList.account_id == current_user.account_id,
         )
     )
     target_list = result.scalar_one_or_none()

backend/app/api/endpoints/trees.py

@@ -1048,6 +1048,7 @@ async def create_tree_share(
     # Create share
     tree_share = TreeShare(
         tree_id=tree.id,
+        account_id=current_user.account_id,
         share_token=share_token,
         created_by=current_user.id,
         allow_forking=share_data.allow_forking,

backend/app/core/audit.py

@@ -12,10 +12,19 @@ async def log_audit(
     resource_type: str,
     resource_id: Optional[UUID] = None,
     details: Optional[dict] = None,
+    account_id: Optional[UUID] = None,
 ) -> None:
     """Record an audit log entry. Does not commit — piggybacks on the caller's commit."""
+    if account_id is None:
+        # Derive from the acting user's account as a fallback (one extra query).
+        from sqlalchemy import select
+        from app.models.user import User
+        result = await db.execute(select(User.account_id).where(User.id == user_id))
+        account_id = result.scalar_one()
+
     entry = AuditLog(
         user_id=user_id,
+        account_id=account_id,
         action=action,
         resource_type=resource_type,
         resource_id=resource_id,

backend/app/models/audit_log.py

@@ -21,6 +21,12 @@ class AuditLog(Base):
         nullable=False,
         index=True
     )
+    account_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("accounts.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True
+    )
     action: Mapped[str] = mapped_column(String(50), nullable=False, index=True)
     resource_type: Mapped[str] = mapped_column(String(50), nullable=False, index=True)
     resource_id: Mapped[Optional[uuid.UUID]] = mapped_column(

backend/app/models/target_list.py

@@ -8,7 +8,6 @@ from app.core.database import Base
 
 if TYPE_CHECKING:
     from app.models.user import User
-    from app.models.team import Team
     from app.models.account import Account
 
 
@@ -18,10 +17,6 @@ class TargetList(Base):
     id: Mapped[uuid.UUID] = mapped_column(
         UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
     )
-    team_id: Mapped[uuid.UUID] = mapped_column(
-        UUID(as_uuid=True), ForeignKey("teams.id", ondelete="CASCADE"),
-        nullable=False, index=True
-    )
     account_id: Mapped[uuid.UUID] = mapped_column(
         UUID(as_uuid=True),
         ForeignKey("accounts.id", ondelete="CASCADE"),

backend/app/models/tree_share.py

@@ -25,6 +25,12 @@ class TreeShare(Base):
         nullable=False,
         index=True
     )
+    account_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("accounts.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True
+    )
     share_token: Mapped[str] = mapped_column(
         String(64),
         unique=True,

backend/app/schemas/target_list.py

@@ -23,7 +23,7 @@ class TargetListUpdate(BaseModel):
 
 class TargetListResponse(BaseModel):
     id: UUID
-    team_id: UUID
+    account_id: UUID
     created_by: Optional[UUID]
     name: str
     description: Optional[str]