feat: persist rate overrides to DB when applying prices in AvailabilityPage

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

src/lib/api.ts

@@ -395,6 +395,15 @@ export const api = {
       req<void>('DELETE', `/api/hotels/${slug}/tariffs/${id}`),
   },
 
+  // ── Rate Overrides (per-cell prices) ─────────────────────────────────────
+  rateOverrides: {
+    list: (slug: string) =>
+      req<RateOverrideApi[]>('GET', `/api/hotels/${slug}/rate-overrides`),
+
+    bulkUpsert: (slug: string, overrides: RateOverridePayload[]) =>
+      req<{ count: number }>('POST', `/api/hotels/${slug}/rate-overrides/bulk`, { overrides }),
+  },
+
   // ── Rate Periods ─────────────────────────────────────────────────────────
   ratePeriods: {
     list: (slug: string) =>
@@ -733,6 +742,26 @@ export interface TariffPayload {
   is_active?: boolean
 }
 
+export interface RateOverrideApi {
+  category_id: string
+  date: string
+  price: number
+  extra_person: number
+  min_nights: number
+  channel_prices: Record<string, number>
+  closed: boolean
+}
+
+export interface RateOverridePayload {
+  category_id: string
+  date: string
+  price: number
+  extra_person?: number
+  min_nights?: number
+  channel_prices?: Record<string, number>
+  closed?: boolean
+}
+
 export interface RatePeriodApi {
   id: string
   name: string