Extend TOTP 2FA to LDAP accounts; disable now requires a code, not a password

2FA was previously local-accounts-only, gated on the assumption that LDAP
already has its own MFA story — that's not actually guaranteed (depends on
what's behind the directory), so app-level TOTP is now available for LDAP
accounts too, as a second factor independent of whatever the directory does
or doesn't enforce. The login route's LDAP branch now checks
user.totpEnabled the same way the local branch already did, routing through
the same login-challenge flow before minting a session.

This forced a change to disabling 2FA: it used to require the current
password, but an LDAP-provisioned user has passwordHash: null — there's no
password to check. Disable now requires a live TOTP code or a recovery
code instead (same "prove you still hold the factor" idea, just checking
the right thing), which works identically for local and LDAP accounts.

Verified: re-ran the full local-account Playwright flow with the new
code-based disable (still passes end-to-end). For the LDAP path — no real
LDAP server available to log in through — flipped a throwaway test account
to authSource="ldap"/passwordHash=null directly in the DB and exercised the
setup/confirm/disable logic functions directly (same technique used
earlier in this session for testing mail ingestion without a live IMAP
server): setup no longer rejects it, confirm and disable both work correctly
with no password present. Test account fully deleted after.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GteWhnWKTmnXcsd5jx6H7u

src/app/api/auth/totp/setup/route.ts

@@ -20,12 +20,6 @@ export async function POST() {
 
   const user = await db.query.users.findFirst({ where: eq(users.id, session.user.id) });
   if (!user) return NextResponse.json({ error: "User not found" }, { status: 404 });
-  if (user.authSource !== "local") {
-    return NextResponse.json(
-      { error: "2FA доступна только для локальных аккаунтов — вход через LDAP защищён на уровне домена" },
-      { status: 400 },
-    );
-  }
 
   const secret = generateTotpSecret();
   await db.update(users).set({ totpSecret: encryptTotpSecret(secret), totpEnabled: false }).where(eq(users.id, user.id));