feat: Phase 1 Group 7 — add account_id to script tables (keep team_id)

team_id is kept in all three tables — drop deferred until app code
is fully migrated off team_id references.

Tables: script_builder_sessions, script_templates, script_generations
Backfill: user_id/created_by → users.account_id

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

backend/alembic/versions/78fc200abac1_add_account_id_script_tables.py

@@ -0,0 +1,80 @@
+"""add account_id to script_builder_sessions, script_templates, script_generations
+
+Revision ID: 78fc200abac1
+Revises: 7f136778f5a8
+Create Date: 2026-04-09 00:00:00.000000
+"""
+from typing import Sequence, Union
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '78fc200abac1'
+down_revision: Union[str, None] = '7f136778f5a8'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    for table in ('script_builder_sessions', 'script_templates', 'script_generations'):
+        op.add_column(table, sa.Column('account_id', sa.UUID(), nullable=True))
+        op.create_foreign_key(
+            f'fk_{table}_account_id', table, 'accounts',
+            ['account_id'], ['id'], ondelete='CASCADE',
+        )
+
+    # script_builder_sessions: user_id → users.account_id
+    op.execute("""
+        UPDATE script_builder_sessions sbs
+        SET account_id = u.account_id
+        FROM users u
+        WHERE sbs.user_id = u.id
+          AND sbs.account_id IS NULL
+    """)
+
+    # script_templates: created_by → users.account_id (nullable created_by)
+    op.execute("""
+        UPDATE script_templates st
+        SET account_id = u.account_id
+        FROM users u
+        WHERE st.created_by = u.id
+          AND st.account_id IS NULL
+    """)
+    # Fallback for script_templates with NULL created_by: team_id → team admin user
+    op.execute("""
+        UPDATE script_templates st
+        SET account_id = u.account_id
+        FROM users u
+        WHERE u.team_id = st.team_id
+          AND u.is_team_admin = TRUE
+          AND u.account_id IS NOT NULL
+          AND st.account_id IS NULL
+    """)
+
+    # script_generations: user_id → users.account_id
+    op.execute("""
+        UPDATE script_generations sg
+        SET account_id = u.account_id
+        FROM users u
+        WHERE sg.user_id = u.id
+          AND sg.account_id IS NULL
+    """)
+
+    # VERIFY
+    for table in ('script_builder_sessions', 'script_templates', 'script_generations'):
+        result = op.get_bind().execute(
+            sa.text(f"SELECT COUNT(*) FROM {table} WHERE account_id IS NULL")
+        )
+        count = result.scalar()
+        if count > 0:
+            raise RuntimeError(f"ROLLBACK: {count} NULL account_id rows in {table}.")
+
+    for table in ('script_builder_sessions', 'script_templates', 'script_generations'):
+        op.alter_column(table, 'account_id', nullable=False)
+        op.create_index(f'ix_{table}_account_id', table, ['account_id'])
+
+
+def downgrade() -> None:
+    for table in ('script_builder_sessions', 'script_templates', 'script_generations'):
+        op.drop_index(f'ix_{table}_account_id', table_name=table)
+        op.drop_constraint(f'fk_{table}_account_id', table, type_='foreignkey')
+        op.drop_column(table, 'account_id')