If a user signs up with their phone number, verifying an email to add to their account doesn't work.

# Bug report - [x] I confirm this is a bug with Supabase, not with my own application. - [x] I confirm I have searched the [Docs](https://docs.supabase.com), GitHub [Discussions](https://github.com/supabase/supabase/discussions), and [Discord](https://discord.supabase.com). ## Describe the bug When a user signs up **with phone number** (OTP) and later tries to **add & verify an email** to the same account during onboarding, the email verification fails with: > `signup is not enabled for otp` (or `OTP signup is not enabled`) This happens **even though OTP signups are enabled** and work for both email-first and phone-first signups individually. The issue appears specific to the **phone-first → add email** path. The reverse flow (**email-first → add phone**) works fine. ## To Reproduce **Auth configuration (Go to settings):** - Email signups: **Enabled** - Phone signups: **Enabled** - External providers: Irrelevant to this repro - “Disable Signups”: **Off** - (Optional) “Confirm email change”: **On** (default behavior) **Steps:** 1. **Sign up with phone** (works) ```ts const { data, error } = await supabase.auth.signInWithOtp({ phone: '+256XXXXXXXXX', // valid phone options: { channel: 'sms' } }); // Receive & verify SMS OTP → user is created/signed in ``` 2. **During onboarding, add an email to the same user** (two common approaches—both end up failing): ** Try email OTP to “verify” the email (alternate path)** ```ts const { error } = await supabase.auth.signInWithOtp({ email: formData.email, options: { shouldCreateUser: false // Don't create a new user, just verify email } }); // Expect: treat as verification of email for existing user // Actual: error "signup is not enabled for otp" ``` 3. **Observe error** shown either directly in the response or surfaced after clicking the email confirmation link / attempting `verifyOtp`: ``` signup is not enabled for otp ``` **Contr…