init: arcadia-admin — admin webapp for arcadia-core, cloned from vibespace

Initial commit. Spun up via the docs/STARTER.md recipe: cp from vibespace,
reset git, rename package, set brand to "Arcadia Admin" with Shield icon
in app/lib/identity.ts.

Inherits the full Crema sibling-lib wiring including @crema/arcadia-client
(typed HTTP + Phoenix Channels realtime against arcadia-core) and
@crema/arcadia-auth-ui (login/signup/password-reset/2FA forms). The /login
route already renders <LoginForm>; <ArcadiaProvider> in app/root.tsx reads
VITE_ARCADIA_URL (default localhost:4000) and VITE_ARCADIA_TENANT (default
"default").

CLAUDE.md and README rewritten to frame this as the admin app for
arcadia-core. docs/STARTER.md removed — arcadia-admin is a leaf consumer,
not a downstream starter.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/routes/login.tsx

@@ -0,0 +1,57 @@
+import { useEffect } from "react"
+import { useNavigate, useSearchParams } from "react-router"
+
+import { LoginForm } from "@crema/arcadia-auth-ui"
+import { useBrand } from "~/lib/identity"
+import { pageTitle } from "~/lib/page-meta"
+import { useSession, persistFromArcadiaLogin } from "~/lib/session"
+
+export const meta = () => pageTitle("Sign in")
+
+export default function LoginRoute() {
+  const navigate = useNavigate()
+  const [params] = useSearchParams()
+  const session = useSession()
+  const brand = useBrand()
+  const BrandIcon = brand.icon
+
+  const next = params.get("next") || "/"
+
+  // Already signed in? Bounce.
+  useEffect(() => {
+    if (session) navigate(next, { replace: true })
+  }, [session, next, navigate])
+
+  return (
+    <div
+      className="relative isolate flex min-h-svh items-center justify-center p-4"
+      style={{ background: "var(--background)" }}
+    >
+      <LoginForm
+        brand={
+          <div className="flex items-center gap-2">
+            <span
+              className="flex size-8 items-center justify-center rounded-lg"
+              style={{ background: "var(--primary)", color: "var(--primary-foreground)" }}
+            >
+              <BrandIcon className="size-4" />
+            </span>
+            <span className="text-sm font-semibold">{brand.name}</span>
+          </div>
+        }
+        heading={`Sign in to ${brand.name}`}
+        subhead="Use your arcadia credentials. In dev seeds: admin@example.com / AdminP@ssw0rd."
+        onSuccess={async ({ tokens, user, twoFactorRequired, twoFactorChallenge }) => {
+          if (twoFactorRequired && twoFactorChallenge) {
+            navigate(`/login/2fa?challenge=${encodeURIComponent(twoFactorChallenge)}&next=${encodeURIComponent(next)}`)
+            return
+          }
+          persistFromArcadiaLogin(tokens, user)
+          navigate(next, { replace: true })
+        }}
+        onForgotPassword={() => navigate("/login/forgot")}
+        onSignup={() => navigate("/signup")}
+      />
+    </div>
+  )
+}