Reorder whole days and insert a day (#589) (#1148)

* feat(days): reorder whole days and insert a day at a position

Adds reorderDays + insertDay to the day service and a PUT /days/reorder route
(plus an optional position on create). Day rows stay stable so a day's
assignments, notes, bookings and accommodations ride along by id; on a dated
trip the calendar dates stay pinned to their slots while the content moves
across them, and each booking's date is re-stamped onto its day's new date
(time-of-day preserved) so day_id stays consistent. Renumbering uses the
two-phase write to avoid the UNIQUE(trip_id, day_number) collision, and a move
that would invert an accommodation's check-in/out span is rejected.

* feat(planner): reorder days from a toolbar popup, and add days

A new toolbar button opens a popup listing the days; drag a row by its grip or
use the up/down arrows to reorder, and add a day from there. Reorders apply
optimistically with rollback and sync over WebSocket; the day headers are left
untouched, so the existing place drop-targets are unaffected.

* i18n: add day-reorder strings across all languages

shared/src/i18n/ja/dayplan.ts

@@ -42,5 +42,14 @@ const dayplan: TranslationStrings = {
   'dayplan.mobile.allAssigned': 'すべて割り当て済み',
   'dayplan.mobile.noMatch': '一致なし',
   'dayplan.mobile.createNew': '新しい場所を作成',
+  'dayplan.reorderDays': '日付を並べ替え',
+  'dayplan.reorderTitle': '日付を並べ替え',
+  'dayplan.reorderHint': 'その日のスポット、メモ、予約も一緒に移動します。',
+  'dayplan.addDay': '日付を追加',
+  'dayplan.moveUp': '上へ移動',
+  'dayplan.moveDown': '下へ移動',
+  'dayplan.reorderUndo': '日付を並べ替え',
+  'dayplan.reorderError': '日付の並べ替えに失敗しました',
+  'dayplan.addDayError': '日付の追加に失敗しました',
 };
 export default dayplan;