feat: Phase 1 Group 5 — add account_id to PSA and notification tables

psa_post_log: backfill via psa_connection, fallback to posted_by user
psa_member_mappings: backfill via psa_connection
notification_logs: backfill via notification_config

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

backend/alembic/versions/8aac5b372402_add_account_id_psa_notifications.py

@@ -0,0 +1,77 @@
+"""add account_id to PSA and notification tables
+
+Revision ID: 8aac5b372402
+Revises: a1d2a84b9abb
+Create Date: 2026-04-09 00:00:00.000000
+"""
+from typing import Sequence, Union
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '8aac5b372402'
+down_revision: Union[str, None] = 'a1d2a84b9abb'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Step 1: ADD COLUMN
+    for table in ('psa_post_log', 'psa_member_mappings', 'notification_logs'):
+        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',
+        )
+
+    # Step 2: BACKFILL
+    # psa_post_log: prefer psa_connection → fallback to posted_by user
+    op.execute("""
+        UPDATE psa_post_log ppl
+        SET account_id = COALESCE(pc.account_id, u.account_id)
+        FROM users u
+        LEFT JOIN psa_connections pc ON pc.id = ppl.psa_connection_id
+        WHERE ppl.posted_by = u.id
+          AND ppl.account_id IS NULL
+    """)
+
+    # psa_member_mappings: via psa_connection
+    op.execute("""
+        UPDATE psa_member_mappings pmm
+        SET account_id = pc.account_id
+        FROM psa_connections pc
+        WHERE pmm.psa_connection_id = pc.id
+          AND pmm.account_id IS NULL
+    """)
+
+    # notification_logs: via notification_config
+    op.execute("""
+        UPDATE notification_logs nl
+        SET account_id = nc.account_id
+        FROM notification_configs nc
+        WHERE nl.notification_config_id = nc.id
+          AND nl.account_id IS NULL
+    """)
+
+    # Step 3: VERIFY
+    for table in ('psa_post_log', 'psa_member_mappings', 'notification_logs'):
+        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}.")
+
+    # Step 4: SET NOT NULL
+    for table in ('psa_post_log', 'psa_member_mappings', 'notification_logs'):
+        op.alter_column(table, 'account_id', nullable=False)
+
+    # Step 5: CREATE INDEX
+    for table in ('psa_post_log', 'psa_member_mappings', 'notification_logs'):
+        op.create_index(f'ix_{table}_account_id', table, ['account_id'])
+
+
+def downgrade() -> None:
+    for table in ('psa_post_log', 'psa_member_mappings', 'notification_logs'):
+        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')