fix(auth): resolve MFA post-activation login failures — tickets #38 #40 #41

#41 (critical): Replace plain Error throws in authorize() with CredentialsSignin
subclasses (MfaRequiredError / MfaRequiredSetupError / InvalidTotpError).
Auth.js v5 forwards CredentialsSignin.code to the client via SignInResponse.code;
plain throws become CallbackRouteError and the message is never visible.
Signin page now checks result.code ?? result.error for exact code matching.

#38: MfaPromptBanner converted to fully client-side component via
trpc.user.getMfaStatus.useQuery() — disappears immediately after MFA enable
without requiring page reload. Snooze key remains userId-scoped via useSession().
Server-side prisma.user.findUnique call removed from (app)/layout.tsx.

#40: NEXTAUTH_URL default fallback removed from docker-compose.yml.
The variable is now required (:?) — docker compose up fails with a descriptive
error if the value is missing, preventing silent localhost redirect bugs.

Tests: auth.test.ts (5), MfaPromptBanner.test.ts (7), reset-password.test.ts (6)
All new tests green. pnpm --filter @capakraken/web exec tsc --noEmit clean.

Co-Authored-By: claude-flow <ruv@ruv.net>

docker-compose.yml

@@ -57,7 +57,7 @@ services:
       # the container itself, not the host.
       DATABASE_URL: postgresql://capakraken:capakraken_dev@postgres:5432/capakraken
       REDIS_URL: redis://redis:6379
-      NEXTAUTH_URL: ${NEXTAUTH_URL:-http://localhost:3100}
+      NEXTAUTH_URL: ${NEXTAUTH_URL:?NEXTAUTH_URL must be set (e.g. https://your-domain.com)}
       NEXTAUTH_SECRET: ${NEXTAUTH_SECRET:?set NEXTAUTH_SECRET}
       # Bypass auth + API rate limiters for E2E test runs only.
       # MUST remain "false" in any production or staging deployment.