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>

apps/web/src/app/auth/signin/page.tsx

@@ -27,30 +27,31 @@ export default function SignInPage() {
     });
 
     if (result?.error) {
-      // Auth.js wraps authorize() errors in the error field
-      if (result.error.includes("MFA_REQUIRED_SETUP")) {
+      // Auth.js v5: CredentialsSignin subclasses forward their `code` via
+      // SignInResponse.code (and sometimes also as result.error).
+      // Check both fields for compatibility across beta versions.
+      const code = result.code ?? result.error;
+
+      if (code === "MFA_REQUIRED_SETUP") {
         // User's role requires MFA but it hasn't been set up yet — redirect to setup
+        setLoading(false);
         router.push("/account/security?mfa_required=1");
         return;
       }
-      if (result.error.includes("MFA_REQUIRED")) {
+      if (code === "MFA_REQUIRED") {
         setMfaRequired(true);
         setLoading(false);
         // Focus the TOTP input after render
         setTimeout(() => totpInputRef.current?.focus(), 100);
         return;
       }
-      if (result.error.includes("INVALID_TOTP")) {
+      if (code === "INVALID_TOTP") {
         setError("Invalid verification code. Please try again.");
         setTotp("");
         setLoading(false);
         return;
       }
-      if (result.error.includes("Too many login attempts")) {
-        setError("Too many login attempts. Please try again later.");
-      } else {
-        setError("Invalid email or password");
-      }
+      setError("Invalid email or password");
       // Reset MFA state on credential error
       if (mfaRequired) {
         setMfaRequired(false);