Validate room-stay bounds on booking expected-date updates

docs/API_REFERENCE.txt

@@ -1822,8 +1822,11 @@ BOOKING APIS
   What it does:
 
   - Updates planned dates on booking (expectedCheckInAt, expectedCheckOutAt), not actual checkout.
+  - Updates booking-level expected dates only; does not auto-change room_stay checkout timestamps.
   - For OPEN bookings: can update both expected check-in and expected check-out.
+  - For OPEN bookings with linked room stays: each stay start/end must remain inside expected booking window.
   - For CHECKED_IN: can update only expectedCheckOutAt (check-in change is blocked).
+  - For CHECKED_IN bookings with linked room stays: stay start must be >= booking check-in and < expected check-out; stay end cannot be after expected check-out.
   - For CHECKED_OUT / CANCELLED / NO_SHOW: returns conflict (Booking closed).
   - Validates range: if both are present, checkout must be after checkin.
   - Returns 204 No Content.
@@ -1853,6 +1856,7 @@ BOOKING APIS
   - 409 Conflict
       - "Cannot change expected check-in after check-in"
       - "Booking closed" for CHECKED_OUT, CANCELLED, NO_SHOW
+      - Room stay bounds outside allowed expected window for OPEN/CHECKED_IN booking
 
 
 - Update booking billing policy API is this one:

src/main/kotlin/com/android/trisolarisserver/controller/booking/BookingFlow.kt

@@ -578,12 +578,65 @@ class BookingFlow(
         if (expectedIn != null && expectedOut != null && !expectedOut.isAfter(expectedIn)) {
             throw ResponseStatusException(HttpStatus.BAD_REQUEST, "Invalid date range")
         }
+        validateRoomStayBoundsForExpectedDatesUpdate(booking, expectedIn, expectedOut)
 
         booking.updatedAt = OffsetDateTime.now()
         bookingRepo.save(booking)
         bookingEvents.emit(propertyId, bookingId)
     }
 
+    private fun validateRoomStayBoundsForExpectedDatesUpdate(
+        booking: com.android.trisolarisserver.models.booking.Booking,
+        expectedIn: OffsetDateTime?,
+        expectedOut: OffsetDateTime?
+    ) {
+        if (expectedIn == null || expectedOut == null) return
+        val bookingId = booking.id ?: return
+        val stays = roomStayRepo.findByBookingId(bookingId)
+        when (booking.status) {
+            BookingStatus.OPEN -> {
+                stays.forEach { stay ->
+                    if (stay.fromAt.isBefore(expectedIn) || stay.fromAt.isAfter(expectedOut)) {
+                        throw ResponseStatusException(
+                            HttpStatus.CONFLICT,
+                            "Room stay start must be within expected check-in/check-out window for OPEN booking"
+                        )
+                    }
+                    val toAt = stay.toAt
+                    if (toAt != null && (toAt.isBefore(expectedIn) || toAt.isAfter(expectedOut))) {
+                        throw ResponseStatusException(
+                            HttpStatus.CONFLICT,
+                            "Room stay end must be within expected check-in/check-out window for OPEN booking"
+                        )
+                    }
+                }
+            }
+            BookingStatus.CHECKED_IN -> {
+                val checkInAt = booking.checkinAt ?: expectedIn
+                stays.forEach { stay ->
+                    if (stay.fromAt.isBefore(checkInAt) || !stay.fromAt.isBefore(expectedOut)) {
+                        throw ResponseStatusException(
+                            HttpStatus.CONFLICT,
+                            "Room stay start must be >= check-in and < expected check-out for CHECKED_IN booking"
+                        )
+                    }
+                    val toAt = stay.toAt
+                    if (toAt != null && toAt.isAfter(expectedOut)) {
+                        throw ResponseStatusException(
+                            HttpStatus.CONFLICT,
+                            "Room stay end cannot be after expected check-out for CHECKED_IN booking"
+                        )
+                    }
+                }
+            }
+            BookingStatus.CHECKED_OUT,
+            BookingStatus.CANCELLED,
+            BookingStatus.NO_SHOW -> {
+                // Already blocked by status guard in updateExpectedDates.
+            }
+        }
+    }
+
     @PostMapping("/{bookingId}/billing-policy")
     @ResponseStatus(HttpStatus.NO_CONTENT)
     @Transactional