feat(auth): Google-only social; sign-up email/password only; phone login entry

- SocialButtons: only Google (Microsoft/Apple hidden).
- Sign-up: remove all social (email/password only).
- Login: keep Google + email/password (single step) + email/SMS OTP; add a direct
  'Sign in with a phone number' entry (SMS OTP), and rename the OTP link to
  'Sign in with a one-time code'. All Supabase-supported; no mandatory 2FA.

src/components/portal/register-flow.tsx

@@ -5,7 +5,7 @@ import { useRouter } from "next/navigation";
 import { Icon, Avatar } from "./icons";
 import {
   StepBack, FlashNote, Badge, OtpBoxes, ResendLink, RememberDevice,
-  SocialButtons, startSocial, PasswordStrength, LegalModal,
+  PasswordStrength, LegalModal,
 } from "./bits";
 import {
   countryCodes, relationshipOptions, addressCountries,
@@ -158,23 +158,13 @@ function StepAccount(p: {
   const [phase, setPhase] = useState<"sso" | "profile">("sso");
   const [modal, setModal] = useState<null | "terms" | "privacy">(null);
 
-  function pickSso(provider: "google" | "microsoft" | "apple") {
-    if (startSocial(provider)) return;
-    const mockEmail = `you@${provider === "microsoft" ? "outlook.com" : provider + ".com"}`;
-    p.setSso({ provider, email: mockEmail });
-    p.setEmail(mockEmail);
-    setPhase("profile");
-  }
-
   if (phase === "sso") {
     const valid = EMAIL_RE.test(p.email);
     return (
       <div>
         <h1>Create your account</h1>
-        <p className="sub">Sign up with a provider or your email to get started.</p>
+        <p className="sub">Enter your email to get started.</p>
         <div style={{ marginTop: 20 }}>
-          <SocialButtons onPick={pickSso} verb="Sign up" />
-          <div className="divider">or continue with email</div>
           <form onSubmit={(e) => { e.preventDefault(); if (valid) { p.setSso(null); setPhase("profile"); } }}>
             <div className="field">
               <label className="label">Email address</label>