feat(site): /start creates an account, not an instance

The form posts to admin's signup and the slug preview goes: there is no
instance at this point, and previewing one promises something the
submission does not create. Creating the instance is now a step in the
portal, which the page's What happens next panel spells out.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

site/components/AccountForm.tsx

@@ -2,20 +2,11 @@
 
 import { useState } from "react";
 import { Honeypot } from "@/components/Honeypot";
-import { submitSignup, type SubmitResult } from "@/lib/submit";
+import { submitAccountSignup, type SubmitResult } from "@/lib/submit";
 
 const MIN_PASSWORD = 12;
 
-function slugify(value: string) {
-    return value
-        .toLowerCase()
-        .trim()
-        .replace(/[^a-z0-9]+/g, "-")
-        .replace(/^-|-$/g, "");
-}
-
-export function InstanceForm() {
-    const [slug, setSlug] = useState("");
+export function AccountForm() {
     const [result, setResult] = useState<SubmitResult>({ state: "idle" });
     const sending = result.state === "sending";
 
@@ -24,8 +15,8 @@ export function InstanceForm() {
         const data = new FormData(event.currentTarget);
         setResult({ state: "sending" });
         setResult(
-            await submitSignup({
-                instance_name: String(data.get("instance_name") ?? ""),
+            await submitAccountSignup({
+                name: String(data.get("name") ?? ""),
                 email: String(data.get("email") ?? ""),
                 password: String(data.get("password") ?? ""),
                 website: String(data.get("website") ?? ""),
@@ -38,7 +29,7 @@ export function InstanceForm() {
             <div role="status">
                 <h2 style={{ fontSize: "var(--s-1)" }}>Check your email.</h2>
                 <p style={{ color: "var(--ink-2)", marginTop: "0.5rem" }}>
-                    We sent a confirmation link. Open it and <b>{slug || "your instance"}</b> is created with you as its owner. The link works once and expires in 24 hours.
+                    We sent a confirmation link. Open it and your Vantage account is ready — then you can create your first instance from the portal. The link works once and expires in 24 hours.
                 </p>
                 <p style={{ color: "var(--ink-3)", marginTop: "0.75rem", fontSize: "0.88rem" }}>
                     Nothing exists until you confirm if the email does not arrive, start again or contact support@hostxtra.co.uk.
@@ -54,14 +45,11 @@ export function InstanceForm() {
             <Honeypot />
 
             <div className="field">
-                <label htmlFor="o-instance">Instance name</label>
-                <input id="o-instance" name="instance_name" type="text" placeholder="Northgate Systems" required onChange={(e) => setSlug(slugify(e.target.value))} aria-describedby="o-instance-err" />
-                <span className="hostline">
-                    <b>{slug || "your-instance"}</b>.vantage.hostxtra.co.uk
-                </span>
-                {fieldError("instance_name") && (
-                    <small id="o-instance-err" className="field__err">
-                        {fieldError("instance_name")}
+                <label htmlFor="o-name">Your organisation</label>
+                <input id="o-name" name="name" type="text" placeholder="Northgate Systems" required aria-describedby="o-name-err" />
+                {fieldError("name") && (
+                    <small id="o-name-err" className="field__err">
+                        {fieldError("name")}
                     </small>
                 )}
             </div>