Resolve ai-service directly from the RAG routes, never the gateway

apps/web/app/api/chat/route.ts

@@ -4,7 +4,13 @@ import type { AnswerBlock, AnswerPlan, Citation, SendMessageResponse } from "@du
 
 export const runtime = "nodejs";
 
-const API_GATEWAY_URL = process.env.API_GATEWAY_URL ?? process.env.AI_SERVICE_URL ?? "http://localhost:8000";
+// RAG never goes through api-gateway. The gateway proxies `/auth/*` only --
+// apps/api-gateway/src/proxy/ holds a single AuthProxyController -- so
+// preferring AI_SERVICE_URL here pointed every RAG call at a service with no
+// such route the moment apiGateway was enabled, breaking chat, suggest,
+// history, sections, section-text and feedback at once. Resolve ai-service
+// directly and let AI_SERVICE_URL mean what its name says: auth only.
+const AI_SERVICE_URL = process.env.AI_SERVICE_URL ?? "http://localhost:8000";
 
 interface RagCitation {
   chunk_id: string;
@@ -257,9 +263,9 @@ export async function POST(request: Request) {
 
   let rag: RagResponse;
   try {
-    const targetUrl = API_GATEWAY_URL.includes("/v1/rag")
-      ? API_GATEWAY_URL
-      : `${API_GATEWAY_URL}/v1/rag/query`;
+    const targetUrl = AI_SERVICE_URL.includes("/v1/rag")
+      ? AI_SERVICE_URL
+      : `${AI_SERVICE_URL}/v1/rag/query`;
 
     const upstreamHeaders: Record<string, string> = {
       "Content-Type": "application/json",
@@ -306,7 +312,7 @@ export async function POST(request: Request) {
       trace_id: `fallback-${Date.now()}`,
       decision: "abstain",
       reason: "upstream_unreachable",
-      answer: `Không thể kết nối đến AI Service (${API_GATEWAY_URL}). Vui lòng đảm bảo AI Service đã được bật.`,
+      answer: `Không thể kết nối đến AI Service (${AI_SERVICE_URL}). Vui lòng đảm bảo AI Service đã được bật.`,
       resolved_drug_id: null,
       citations: [],
     };