T01: core infrastructure + auth + multi-tenant + RLS

- 10 models: tenants, users, user_tenants, roles, sessions, audit_log, deletion_log, notifications, password_reset_tokens, api_tokens
- Session-based auth (Redis + PostgreSQL audit trail)
- Multi-tenant with ORM-level filtering + PostgreSQL RLS (set_config)
- RBAC with roles/permissions + field-level permissions
- CSRF protection via Origin header validation
- Auth rate limiting (Redis counters with TTL)
- CORS with explicit origins (no wildcard)
- Health endpoint (no auth required)
- Notification service + audit log middleware
- 29 tests, 26 ACs, all passing
- Coverage: 62% (infrastructure modules pending coverage in later tasks)

alembic/script.py.mako

@@ -3,18 +3,14 @@
 Revision ID: ${up_revision}
 Revises: ${down_revision | comma,n}
 Create Date: ${create_date}
-
 """
-from __future__ import annotations
 
-from collections.abc import Sequence
-from typing import Union
+from typing import Sequence, Union
 
 from alembic import op
 import sqlalchemy as sa
 ${imports if imports else ""}
 
-# revision identifiers, used by Alembic.
 revision: str = ${repr(up_revision)}
 down_revision: Union[str, None] = ${repr(down_revision)}
 branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}