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/common.py

@@ -1,30 +1,36 @@
-"""Common Pydantic schemas: pagination."""
+"""Common schemas for pagination, errors, etc."""
 
 from __future__ import annotations
 
-from typing import Generic, TypeVar
-
-from pydantic import BaseModel, ConfigDict, Field
-
-T = TypeVar("T")
+from pydantic import BaseModel
 
 
-class PaginationParams(BaseModel):
-    """Standard pagination query params."""
-
-    skip: int = Field(default=0, ge=0)
-    limit: int = Field(default=20, ge=1, le=100)
+class ErrorResponse(BaseModel):
+    detail: str
+    code: str | None = None
+    fields: dict[str, str] | None = None
 
 
-class PaginatedResponse(BaseModel, Generic[T]):
-    """Generic paginated response."""
+class HealthResponse(BaseModel):
+    status: str
+    version: str
 
-    model_config = ConfigDict(from_attributes=True)
 
-    items: list[T]  # type: ignore[valid-type]
+class NotificationResponse(BaseModel):
+    id: str
+    type: str
+    title: str
+    body: str | None = None
+    read_at: str | None = None
+    created_at: str | None = None
+
+
+class NotificationListResponse(BaseModel):
+    items: list[NotificationResponse]
     total: int
-    skip: int
-    limit: int
+    page: int
+    page_size: int
 
 
-__all__ = ["PaginatedResponse", "PaginationParams"]
+class UnreadCountResponse(BaseModel):
+    count: int