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/schemas/tenant.py

@@ -0,0 +1,20 @@
+"""Tenant schemas."""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field
+
+
+class TenantCreate(BaseModel):
+    name: str = Field(..., min_length=1, max_length=200)
+    slug: str = Field(..., min_length=1, max_length=100)
+
+
+class TenantResponse(BaseModel):
+    id: str
+    name: str
+    slug: str
+
+
+class TenantUserAssign(BaseModel):
+    user_id: str = Field(..., min_length=1)