fix(trips): preserve day content when setting dates on dateless trips

Dateless days are now reassigned to the new date range instead of being
deleted and recreated. This keeps all assignments, notes, bookings and
other day content intact when a user adds start/end dates to a trip
that was created without them.

server/src/services/tripService.ts

@@ -75,9 +75,13 @@ export function generateDays(tripId: number | bigint | string, startDate: string
   const targetDateSet = new Set(targetDates);
 
   const toDelete = existing.filter(d => d.date && !targetDateSet.has(d.date));
-  const datelessToDelete = existing.filter(d => !d.date);
+  const dateless = existing.filter(d => !d.date).sort((a, b) => a.day_number - b.day_number);
   const del = db.prepare('DELETE FROM days WHERE id = ?');
-  for (const d of [...toDelete, ...datelessToDelete]) del.run(d.id);
+  for (const d of toDelete) del.run(d.id);
+
+  // Reassign dateless days to the first unmatched target dates (preserves content)
+  const assignDate = db.prepare('UPDATE days SET date = ?, day_number = ? WHERE id = ?');
+  let datelessIdx = 0;
 
   const setTemp = db.prepare('UPDATE days SET day_number = ? WHERE id = ?');
   const kept = existing.filter(d => d.date && targetDateSet.has(d.date));
@@ -91,10 +95,17 @@ export function generateDays(tripId: number | bigint | string, startDate: string
     const ex = existingByDate.get(date);
     if (ex) {
       update.run(i + 1, ex.id);
+    } else if (datelessIdx < dateless.length) {
+      // Reuse a dateless day — keeps its assignments, notes, etc.
+      assignDate.run(date, i + 1, dateless[datelessIdx].id);
+      datelessIdx++;
     } else {
       insert.run(tripId, i + 1, date);
     }
   }
+
+  // Delete any remaining unused dateless days
+  for (let i = datelessIdx; i < dateless.length; i++) del.run(dateless[i].id);
 }
 
 // ── Trip CRUD ─────────────────────────────────────────────────────────────