feat: Phase 1 Group 6 — add account_id to maintenance_schedules

Primary backfill: tree_id → trees.account_id
Fallback: created_by → users.account_id (for is_default tree rows)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/alembic/versions/7f136778f5a8_add_account_id_maintenance.py

@@ -0,0 +1,62 @@
+"""add account_id to maintenance_schedules
+
+Revision ID: 7f136778f5a8
+Revises: 8aac5b372402
+Create Date: 2026-04-09 00:00:00.000000
+"""
+from typing import Sequence, Union
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '7f136778f5a8'
+down_revision: Union[str, None] = '8aac5b372402'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column('maintenance_schedules',
+                  sa.Column('account_id', sa.UUID(), nullable=True))
+    op.create_foreign_key(
+        'fk_maintenance_schedules_account_id', 'maintenance_schedules', 'accounts',
+        ['account_id'], ['id'], ondelete='CASCADE',
+    )
+
+    # Primary: tree_id → trees.account_id (only where tree.account_id is NOT NULL)
+    op.execute("""
+        UPDATE maintenance_schedules ms
+        SET account_id = t.account_id
+        FROM trees t
+        WHERE ms.tree_id = t.id
+          AND t.account_id IS NOT NULL
+          AND ms.account_id IS NULL
+    """)
+
+    # Fallback: created_by → users.account_id (for is_default trees with NULL account_id)
+    op.execute("""
+        UPDATE maintenance_schedules ms
+        SET account_id = u.account_id
+        FROM users u
+        WHERE ms.created_by = u.id
+          AND u.account_id IS NOT NULL
+          AND ms.account_id IS NULL
+    """)
+
+    result = op.get_bind().execute(
+        sa.text("SELECT COUNT(*) FROM maintenance_schedules WHERE account_id IS NULL")
+    )
+    count = result.scalar()
+    if count > 0:
+        raise RuntimeError(
+            f"ROLLBACK: {count} maintenance_schedules rows have NULL account_id. "
+            "Check if created_by is NULL — those rows need manual resolution."
+        )
+
+    op.alter_column('maintenance_schedules', 'account_id', nullable=False)
+    op.create_index('ix_maintenance_schedules_account_id', 'maintenance_schedules', ['account_id'])
+
+
+def downgrade() -> None:
+    op.drop_index('ix_maintenance_schedules_account_id', table_name='maintenance_schedules')
+    op.drop_constraint('fk_maintenance_schedules_account_id', 'maintenance_schedules', type_='foreignkey')
+    op.drop_column('maintenance_schedules', 'account_id')

backend/app/models/maintenance_schedule.py

@@ -23,6 +23,12 @@ class MaintenanceSchedule(Base):
     created_by: Mapped[Optional[uuid.UUID]] = mapped_column(
         UUID(as_uuid=True), ForeignKey("users.id", ondelete="SET NULL"), nullable=True
     )
+    account_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("accounts.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
     cron_expression: Mapped[str] = mapped_column(String(100), nullable=False)
     timezone: Mapped[str] = mapped_column(String(100), nullable=False, default="UTC")
     target_list_id: Mapped[Optional[uuid.UUID]] = mapped_column(

backend/tests/test_phase1_migrations.py

@@ -381,3 +381,42 @@ async def test_psa_member_mapping_account_id_matches_connection(test_db: AsyncSe
     )
     row = result.scalar_one()
     assert row.account_id == account.id
+
+
+# ── Group 6: Maintenance ──────────────────────────────────────────────────────
+
+@pytest.mark.asyncio
+async def test_maintenance_schedule_account_id_matches_tree(test_db: AsyncSession):
+    """maintenance_schedules.account_id must match the tree's account_id."""
+    from app.models.maintenance_schedule import MaintenanceSchedule
+
+    account, user = await _make_account_and_user(test_db, "ms1")
+    tree = Tree(
+        name="Maintenance Flow",
+        account_id=account.id,
+        author_id=user.id,
+        visibility="team",
+        tree_type="maintenance",
+        tree_structure={"id": "root", "type": "start", "children": []},
+        is_active=True,
+        status="published",
+    )
+    test_db.add(tree)
+    await test_db.flush()
+
+    schedule = MaintenanceSchedule(
+        tree_id=tree.id,
+        account_id=account.id,
+        created_by=user.id,
+        cron_expression="0 9 * * 1",
+        timezone="UTC",
+        is_active=True,
+    )
+    test_db.add(schedule)
+    await test_db.commit()
+
+    result = await test_db.execute(
+        select(MaintenanceSchedule).where(MaintenanceSchedule.id == schedule.id)
+    )
+    row = result.scalar_one()
+    assert row.account_id == account.id