Let a household choose to be paid for the red days

Asking for a full week off never spent anything on the Saturday, the
Sunday or a holiday, and a test now says so outright rather than leaving
it to be rediscovered. Those days are free because vacation cannot be
taken on a day that is not a working day.

Parental benefit is a payment rather than a schedule, though, so it can
be drawn on a red day to turn an unpaid day off into a paid one — at the
cost of a day the family would otherwise keep. That is now a workspace
setting, off by default, and it never reaches for a vacation day. With it
off the planner behaves exactly as before.

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

backend/tests/unit/test_workspace_service.py

@@ -69,6 +69,30 @@ class TestWorkspaceUpdate:
         with pytest.raises(NotFoundError):
             await workspace_service.update_workspace(uuid4(), name="Whatever")
 
+    async def test_take_pl_on_red_days_defaults_to_false(
+        self,
+        workspace_service: WorkspaceService,
+    ) -> None:
+        ws = await workspace_service.create_workspace("New Workspace")
+        assert ws.take_pl_on_red_days is False
+
+    async def test_update_take_pl_on_red_days(
+        self,
+        workspace_service: WorkspaceService,
+    ) -> None:
+        ws = await workspace_service.create_workspace("Workspace")
+        updated = await workspace_service.update_workspace(ws.id, take_pl_on_red_days=True)
+        assert updated.take_pl_on_red_days is True
+
+        # Persisted, not just returned in-memory -- re-fetch to be sure.
+        refetched = await workspace_service.get_workspace(ws.id)
+        assert refetched.take_pl_on_red_days is True
+
+        # `None` (the default) means "leave unchanged", mirroring `name`'s
+        # omit-to-keep convention.
+        unchanged = await workspace_service.update_workspace(ws.id, name="Renamed")
+        assert unchanged.take_pl_on_red_days is True
+
 
 class TestRenameMember:
     """Rename a workspace member's display name (placeholder or self)."""