feat(provisioning): provisioning UI — signup, invites, accept page, unlink

Phase 6: the UI for the Phase 5 provisioning backend.

- CreateGameAccountForm: reusable game-account form (own username + password),
  mapping the sidecar errors (409/429/403/503) to friendly messages. Wired into
  GameAccounts (self-serve) — shown alongside the [link flow when the
  game_account_signup flag is on (exposed via public settings), so a registered
  player can create + link a game account from their portal.
- Admin Invites view (/admin/invites, admin-only): send an invite at a chosen
  access level, list invites with status, revoke pending ones. When email isn't
  configured the create response's accept link is surfaced to copy manually.
- Public accept page (/invite/:token): validates the invite, sets username +
  password (email + role pre-assigned), creates the account at that role and logs
  in; for a player invite it then offers the built-in "create game account" step
  before the portal. Honeypot-guarded like registration.
- Admin unlink wired into UserDetail via GameAccounts (per-account Unlink button,
  confirm + reconcile).
- Backend: expose gameAccountSignup availability in public settings.

Client build clean; server 193/193.

Refs .plans/protocol2-integration.md (Phase 6). Completes the Protocol 2.0/2.1 integration.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/src/components/CreateGameAccountForm.jsx

@@ -0,0 +1,69 @@
+import { useState } from 'react'
+
+// Reusable "create a game account" form (its own username + password — the game
+// client credentials, distinct from the website login). Calls `submit(account,
+// password)` which should POST /player/shard/account; on success calls onCreated.
+// Used by the player portal (self-serve) and the invite-accept page alike.
+export default function CreateGameAccountForm({ submit, onCreated, compact = false }) {
+  const [account, setAccount] = useState('')
+  const [password, setPassword] = useState('')
+  const [busy, setBusy] = useState(false)
+  const [msg, setMsg] = useState('')
+  const [error, setError] = useState('')
+
+  async function onSubmit(e) {
+    e.preventDefault()
+    setMsg(''); setError('')
+    if (!/^[A-Za-z0-9][A-Za-z0-9_.-]{2,29}$/.test(account)) {
+      return setError('Account name must be 3–30 letters, numbers, . _ or -.')
+    }
+    if (password.length < 8) return setError('Password must be at least 8 characters.')
+    setBusy(true)
+    try {
+      await submit(account, password)
+      setMsg(`Game account “${account}” created and linked.`)
+      setAccount(''); setPassword('')
+      if (onCreated) await onCreated()
+    } catch (err) {
+      if (err.status === 409) setError('That account name is already taken.')
+      else if (err.status === 429) setError('The account limit for your network has been reached.')
+      else if (err.status === 403) setError('Game-account signup is not available right now.')
+      else if (err.status === 503) setError('The game server is unavailable — try again shortly.')
+      else setError(err.message || 'Could not create the account right now.')
+    } finally {
+      setBusy(false)
+    }
+  }
+
+  return (
+    <form onSubmit={onSubmit}>
+      {!compact && (
+        <p className="sans" style={{ marginTop: 0, color: 'var(--muted)', fontSize: '0.88rem', lineHeight: 1.6 }}>
+          Choose the username and password you’ll type into the game client. These are your
+          <strong style={{ color: 'var(--head)' }}> game</strong> credentials — separate from your website login.
+        </p>
+      )}
+      <label style={{ display: 'block', marginBottom: 14 }}>
+        <span className="field-label">Game account name</span>
+        <input
+          type="text" autoComplete="off" value={account}
+          onChange={(e) => setAccount(e.target.value)} className="input" placeholder="e.g. darrow"
+        />
+      </label>
+      <label style={{ display: 'block', marginBottom: 16 }}>
+        <span className="field-label">Game password</span>
+        <input
+          type="password" autoComplete="new-password" value={password}
+          onChange={(e) => setPassword(e.target.value)} className="input"
+        />
+      </label>
+
+      {error && <p className="sans" style={{ margin: '0 0 12px', color: '#d98b84', fontSize: '0.85rem' }}>{error}</p>}
+      {msg && <p className="sans" style={{ margin: '0 0 12px', color: '#7fd0a4', fontSize: '0.85rem' }}>{msg}</p>}
+
+      <button type="submit" disabled={busy} className="btn btn-primary btn-sq">
+        {busy ? 'Creating…' : 'Create game account'}
+      </button>
+    </form>
+  )
+}