fix(rectification): surface pricing failures and persist opening question

frontend/src/app/api/consult/route.ts

@@ -30,7 +30,7 @@ import {
 } from "@/lib/consultation-entrypoint";
 import { CreditRpcError } from "@/lib/consultation-billing";
 import { cachedSystemMessage, mergePromptCacheUsage, promptCacheUsage } from "@/lib/agent-generation-settings";
-import { resolveFeaturePricing } from "@/lib/feature-pricing";
+import { FeaturePricingError, resolveFeaturePricing } from "@/lib/feature-pricing";
 import { reserveConsultationModel } from "@/lib/consultation-model-selection";
 import { resolveSessionLanguageModel } from "@/lib/model-catalog";
 import { createAdminSupabaseClient } from "@/lib/supabase/admin";
@@ -393,6 +393,19 @@ export async function POST(request: Request) {
       ),
     });
   } catch (error) {
+    if (error instanceof FeaturePricingError) {
+      console.error(
+        `[billing] reservation failed request=${requestId} reason=${error.code}`,
+      );
+      return NextResponse.json(
+        {
+          error: "计费配置不可用",
+          message: "当前服务的计费配置尚未完成，请联系支持人员，本次不会扣点。",
+          code: "pricing_configuration_unavailable",
+        },
+        { status: 503 },
+      );
+    }
     if (error instanceof ConsultationPlanValidationError) {
       return NextResponse.json(
         {