feat(backend): add durable MAX linking and notification queue

Refs #82

app/db/bootstrap.py

@@ -5,6 +5,7 @@ The only module (besides registration code) that touches both schemas — and on
 
 from app.db import audit as _audit  # noqa: F401  (registers audit_log in clinical metadata)
 from app.db import intake as _intake  # noqa: F401
+from app.db import max_notifications as _max_notifications  # noqa: F401
 from app.db import scheduler as _scheduler  # noqa: F401
 from app.db.clinical import ClinicalBase
 from app.db.identity import IdentityBase

app/db/max_notifications.py

@@ -0,0 +1,50 @@
+"""MAX identifiers and delivery metadata live only in the identity DB; no medical message bodies."""
+
+from datetime import datetime
+
+from sqlalchemy import BigInteger, Boolean, Integer, String
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.db.identity import IdentityBase
+from app.db.types import TZDateTime
+
+
+class MaxBinding(IdentityBase):
+    __tablename__ = "max_bindings"
+
+    # No FK: anonymous web profiles intentionally have no patients row in identity.
+    token: Mapped[str] = mapped_column(String(64), primary_key=True)
+    user_id: Mapped[int] = mapped_column(BigInteger, unique=True)
+    enabled: Mapped[bool] = mapped_column(Boolean, default=True)
+    connected_at: Mapped[datetime] = mapped_column(TZDateTime)
+
+
+class MaxLinkCode(IdentityBase):
+    __tablename__ = "max_link_codes"
+
+    digest: Mapped[str] = mapped_column(String(64), primary_key=True)
+    token: Mapped[str] = mapped_column(String(64), unique=True)
+    expires_at: Mapped[datetime] = mapped_column(TZDateTime, index=True)
+    used_at: Mapped[datetime | None] = mapped_column(TZDateTime)
+
+
+class MaxReceipt(IdentityBase):
+    __tablename__ = "max_webhook_receipts"
+
+    digest: Mapped[str] = mapped_column(String(64), primary_key=True)
+    received_at: Mapped[datetime] = mapped_column(TZDateTime, index=True)
+
+
+class MaxDelivery(IdentityBase):
+    __tablename__ = "max_deliveries"
+
+    id: Mapped[str] = mapped_column(String(64), primary_key=True)
+    token: Mapped[str | None] = mapped_column(String(64), index=True)
+    user_id: Mapped[int] = mapped_column(BigInteger)
+    kind: Mapped[str] = mapped_column(String(24))
+    state: Mapped[str] = mapped_column(String(16), default="queued", index=True)
+    attempts: Mapped[int] = mapped_column(Integer, default=0)
+    created_at: Mapped[datetime] = mapped_column(TZDateTime)
+    next_attempt_at: Mapped[datetime] = mapped_column(TZDateTime, index=True)
+    lease: Mapped[str | None] = mapped_column(String(32))
+    error_code: Mapped[str | None] = mapped_column(String(32))