Fix booking creation: localStorage token, conflict detection, paid_amount

- Fix api.ts getToken/saveToken to read from localStorage (matching AuthContext) — was reading sessionStorage causing all API requests to fail auth until refresh
- Fix session cleanup on 401 to use localStorage
- Add isConflict/availableRooms helpers to BookingModal; show amber warning when selected room is occupied with clickable free room suggestions
- Pass bookings prop to BookingModal via BookingCalendar
- Add paid_amount to backend POST /bookings INSERT
- Show alert() when booking creation fails so user sees the error
- Pass paidAmount in CalendarPage handleCreate

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

backend/src/routes/bookings.ts

@@ -58,7 +58,7 @@ const bookings: FastifyPluginAsync = async (fastify) => {
   fastify.post<SlugParam & { Body: {
     room_id: string; guest_name: string; guest_email?: string; guest_phone?: string
     check_in: string; check_out: string; adults?: number; children?: number
-    status?: string; source?: string; total_amount?: number; notes?: string
+    status?: string; source?: string; total_amount?: number; paid_amount?: number; notes?: string
   } }>(
     '/api/hotels/:slug/bookings',
     { onRequest: [fastify.authenticate] },
@@ -76,7 +76,7 @@ const bookings: FastifyPluginAsync = async (fastify) => {
       const {
         room_id, guest_name, guest_email, guest_phone,
         check_in, check_out, adults = 1, children = 0,
-        status = 'confirmed', source = 'direct', total_amount, notes,
+        status = 'confirmed', source = 'direct', total_amount, paid_amount = 0, notes,
       } = request.body
 
       // Check for conflicts
@@ -88,17 +88,17 @@ const bookings: FastifyPluginAsync = async (fastify) => {
         [room_id, check_out, check_in],
       )
       if (conflicts.length > 0) {
-        return reply.code(409).send({ error: 'Room already booked for these dates' })
+        return reply.code(409).send({ error: 'Номер уже занят на эти даты' })
       }
 
       const { rows } = await db.query(
         `INSERT INTO bookings
            (hotel_id, room_id, guest_name, guest_email, guest_phone, check_in, check_out,
-            adults, children, status, source, total_amount, notes)
-         VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13) RETURNING *`,
+            adults, children, status, source, total_amount, paid_amount, notes)
+         VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14) RETURNING *`,
         [hotelId, room_id, guest_name, guest_email ?? null, guest_phone ?? null,
          check_in, check_out, adults, children, status, source,
-         total_amount ?? null, notes ?? null],
+         total_amount ?? 0, paid_amount, notes ?? null],
       )
       return reply.code(201).send(rows[0])
     },