Let a day removed from a period stay removed

Taking one day out of a period the planner placed did nothing that
lasted: the period still asked for a full week, so the next sync put the
day straight back. The option was disabled rather than lying about it.

A removed day is now recorded as its own thing — no leave for this
parent, this child, this date — and the planner honours it on every
later sync. It is kept apart from the working-day overrides, which
answer a different question about the calendar rather than about the
plan.

The day belongs to the parent whose band was clicked, so removing one
parent's day leaves their partner's alone; where both parents were to be
off on one funding arrangement, the partner is simply funded on their
own instead. A removed day shortens what the period is asking for rather
than counting as a day the plan failed to find, so the advice about
closing a shortfall does not start arguing for a day nobody wants.

Nothing is removed without a way back: the toast undoes it, and the day
itself is marked in the calendar and offers to restore.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ei7gCZzdd751uZtPzb1Pep

backend/app/models/planned_day_exclusion.py

@@ -0,0 +1,42 @@
+"""API schemas (Pydantic) for PlannedDayExclusion.
+
+Schemas are the API boundary — they validate request bodies and shape
+responses, kept separate from the domain entity so the wire format can
+evolve independently.
+"""
+
+from datetime import date, datetime
+from uuid import UUID
+
+from pydantic import BaseModel
+
+from app.entities.planned_day_exclusion import PlannedDayExclusion
+
+
+class PlannedDayExclusionCreate(BaseModel):
+    workspace_id: UUID
+    child_id: UUID
+    parent_personal_data_uuid: UUID
+    date: date
+
+
+class PlannedDayExclusionResponse(BaseModel):
+    id: UUID
+    workspace_id: UUID
+    child_id: UUID
+    parent_personal_data_uuid: UUID
+    date: date
+    created_at: datetime | None
+    updated_at: datetime | None
+
+    @classmethod
+    def from_entity(cls, entity: PlannedDayExclusion) -> "PlannedDayExclusionResponse":
+        return cls(
+            id=entity.id,
+            workspace_id=entity.workspace_id,
+            child_id=entity.child_id,
+            parent_personal_data_uuid=entity.parent_personal_data_uuid,
+            date=entity.date,
+            created_at=entity.created_at,
+            updated_at=entity.updated_at,
+        )