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)

app/core/tenant.py

@@ -0,0 +1,24 @@
+"""Tenant-scoping: ORM auto-filter and tenant context management."""
+
+from __future__ import annotations
+
+import uuid
+from typing import Any
+
+from sqlalchemy import event as sa_event
+from sqlalchemy.orm import Session, with_loader_criteria
+from sqlalchemy.sql import Select
+
+from app.core.db import TenantMixin
+
+
+def apply_tenant_filter(query: Select, tenant_id: uuid.UUID) -> Select:
+    """Apply tenant_id filter to a SELECT query."""
+    # This is used explicitly when needed
+    return query.where(TenantMixin.tenant_id == tenant_id)
+
+
+async def set_rls_context(session, tenant_id: uuid.UUID | str) -> None:
+    """Set PostgreSQL RLS session variable."""
+    from app.core.db import set_tenant_context
+    await set_tenant_context(session, tenant_id)