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

frontend/src/components/modals/PlannedDayModal.tsx

@@ -23,6 +23,12 @@ export interface PlannedDayModalSavePinnedPayload {
   isDubbeldag: boolean
 }
 
+/** One day the user removed by hand, ready to be offered back. */
+export interface PlannedDayExclusionEntry {
+  id: string
+  parentName: string
+}
+
 export interface PlannedDayModalProps {
   date: string
   isOpen: boolean
@@ -39,6 +45,11 @@ export interface PlannedDayModalProps {
   onSaveWish: (payload: PlannedDayModalSaveWishPayload) => Promise<void>
   onSavePinned: (payload: PlannedDayModalSavePinnedPayload) => Promise<void>
   onDelete?: (() => Promise<void>) | undefined
+  /** Removals recorded for THIS date (see `PlannedDayExclusion`), one per
+   * parent. Shown with a way back: a day the user can't restore is a trap,
+   * and the undo toast is gone as soon as it times out. */
+  excludedEntries?: PlannedDayExclusionEntry[] | undefined
+  onRestoreExcluded?: ((exclusionId: string) => Promise<void>) | undefined
   onClose: () => void
   isSaving?: boolean | undefined
   error?: string | null | undefined
@@ -57,6 +68,8 @@ export function PlannedDayModal({
   onSaveWish,
   onSavePinned,
   onDelete,
+  excludedEntries = [],
+  onRestoreExcluded,
   onClose,
   isSaving = false,
   error = null,
@@ -217,6 +230,28 @@ export function PlannedDayModal({
             </div>
           )}
 
+          {!isRangeMode &&
+            excludedEntries.map((entry) => (
+              <div
+                key={entry.id}
+                className="planned-day-modal__excluded-notice"
+                data-testid="excluded-notice"
+              >
+                <span>{t('plannedDayModal.excludedNotice', { parent: entry.parentName })}</span>
+                {onRestoreExcluded && (
+                  <button
+                    type="button"
+                    className="btn btn--secondary btn--sm"
+                    onClick={() => void onRestoreExcluded(entry.id)}
+                    disabled={isSaving}
+                    data-testid={`restore-excluded-${entry.id}`}
+                  >
+                    {t('plannedDayModal.restoreExcludedButton')}
+                  </button>
+                )}
+              </div>
+            ))}
+
           <div className="stack">
             {!forcedAdvanced && hasMultipleParents && (
               <div className="field">