fix(auth): use public URL for magic-link redirects

apps/web/src/app/auth/discord/route.ts

@@ -3,6 +3,7 @@ import { createAuthRepository, ipObservations, recordEvent } from "@minecraft-ac
 import { getClientIp } from "@minecraft-account-manager/network";
 import type { NextRequest } from "next/server";
 import { NextResponse } from "next/server";
+import { applicationUrl } from "@/lib/application-url";
 import { db } from "@/lib/database";
 import { getIpIntelligence, toAuditIpData } from "@/lib/ip-intelligence";
 
@@ -38,7 +39,7 @@ export async function GET(request: NextRequest) {
     ]);
 
     const destination = result.user.firstName ? "/account" : "/welcome";
-    const response = NextResponse.redirect(new URL(destination, request.url));
+    const response = NextResponse.redirect(applicationUrl(destination));
     response.cookies.set(SESSION_COOKIE_NAME, result.sessionToken, {
       httpOnly: true,
       secure: process.env.NODE_ENV === "production",
@@ -49,7 +50,7 @@ export async function GET(request: NextRequest) {
     return response;
   } catch (error) {
     if (error instanceof InvalidLoginCodeError) {
-      return NextResponse.redirect(new URL("/auth/error", request.url));
+      return NextResponse.redirect(applicationUrl("/auth/error"));
     }
     throw error;
   }

apps/web/src/lib/application-url.test.ts

@@ -0,0 +1,9 @@
+import { describe, expect, it } from "vitest";
+import { applicationUrl } from "./application-url";
+
+describe("applicationUrl", () => {
+  it("builds browser redirects from the configured public application URL", () => {
+    expect(applicationUrl("/welcome", "https://portal.somc.club"))
+      .toEqual(new URL("https://portal.somc.club/welcome"));
+  });
+});

apps/web/src/lib/application-url.ts

@@ -0,0 +1,4 @@
+export function applicationUrl(path: string, baseUrl = process.env.APP_URL) {
+  if (!baseUrl) throw new Error("APP_URL is required to build public application URLs");
+  return new URL(path, baseUrl);
+}