Add date editing with conflict detection and rental booking editing

- BookingDetailPanel: edit dates/room with inline conflict detection; options to force-save or swap conflicting booking's room
- BookingsPage + CalendarPage: pass rooms/allBookings/onBulkUpdate to panel
- RentalBookingModal: accept editBooking prop to pre-populate fields for editing
- RentalPage: add edit (pencil) button per booking row, unify create/update handler

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/BookingsPage.tsx

@@ -363,11 +363,21 @@ export function BookingsPage() {
         <BookingDetailPanel
           booking={selected}
           room={room(selected.roomId)}
+          rooms={MOCK_ROOMS}
+          allBookings={bookings}
           onClose={() => setSelected(null)}
           onUpdate={(id, data) => {
             setBookings(prev => prev.map(b => b.id === id ? { ...b, ...data } : b))
             setSelected(null)
           }}
+          onBulkUpdate={(updates) => {
+            setBookings(prev => {
+              let next = [...prev]
+              updates.forEach(u => { next = next.map(b => b.id === u.id ? { ...b, ...u.data } : b) })
+              return next
+            })
+            setSelected(null)
+          }}
         />
       )}