Step 4: Add admin UI page for pricing configuration

- Add pricing API functions to admin.ts
- Create admin pricing page with form and validation
- Add MANAGE_PRICING permission to auth context
- Add pricing to admin navigation
- Add translations for pricing page (en, ca, es)
- Update PageLayout and Header types for new page

frontend/app/api/admin.ts

@@ -6,6 +6,8 @@ type PaginatedInvites = components["schemas"]["PaginatedResponse_InviteResponse_
 type AdminExchangeResponse = components["schemas"]["AdminExchangeResponse"];
 type AvailabilityResponse = components["schemas"]["AvailabilityResponse"];
 type PriceHistoryRecord = components["schemas"]["PriceHistoryResponse"];
+type PricingConfigResponse = components["schemas"]["PricingConfigResponse"];
+type PricingConfigUpdate = components["schemas"]["PricingConfigUpdate"];
 
 interface CreateInviteRequest {
   godfather_id: number;
@@ -153,4 +155,18 @@ export const adminApi = {
   fetchPrice(): Promise<PriceHistoryRecord> {
     return client.post<PriceHistoryRecord>("/api/audit/price-history/fetch", {});
   },
+
+  /**
+   * Get current pricing configuration
+   */
+  getPricingConfig(): Promise<PricingConfigResponse> {
+    return client.get<PricingConfigResponse>("/api/admin/pricing");
+  },
+
+  /**
+   * Update pricing configuration
+   */
+  updatePricingConfig(request: PricingConfigUpdate): Promise<PricingConfigResponse> {
+    return client.put<PricingConfigResponse>("/api/admin/pricing", request);
+  },
 };