fix(preview): switch spec generation to Haiku 4.5 to fit the proxy window

Sonnet still overran Cloudflare's edge timeout — the 504 fired at 90s but
the proxy had already cut the connection, so the browser saw a headerless
524 reported as a CORS error.

Measured against the live API: Haiku 4.5 generates the spec at ~200 tok/s,
so a full 8k-token spec completes in ~40s. With a hard 60s timeout and no
retries the route is guaranteed to answer well inside the proxy window.

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

apps/web/app/(dashboard)/servers/new/page.tsx

@@ -457,7 +457,7 @@ function NewServerPageInner() {
           <Loader2 className="mx-auto animate-spin text-[--color-accent]" size={22} />
           <p className="mt-4 text-[13px]">Analyzing your prompt…</p>
           <p className="mt-1 text-[12px] text-[--color-fg-subtle]">
-            Claude Sonnet 4.6 is drafting the tool spec. Usually 20–40 seconds.
+            Claude is drafting the tool spec. Usually 15–40 seconds.
           </p>
           <p className="mono mt-3 text-[11px] tabular-nums text-[--color-fg-muted]">
             {elapsedSec}s elapsed