refactor: flatten monorepo to single web package (#12)

Flatten the pnpm monorepo (apps/web + packages/*) into a single web package at the repo root.

- Move app/lib/components/scripts/public to root; drop apps/web and packages/* wrappers
- Rewrite tsconfig paths (@infiplot/*) to ./lib/*; turbopack.root = __dirname
- Update Vercel (no root-directory) and Cloudflare (pnpm build:cf at root) deploy paths
- Regenerate pnpm-lock.yaml to drop stale workspace importers
- Bump engines.node to >=22 to match wrangler

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/api/scene/route.ts

@@ -0,0 +1,33 @@
+import { requestScene } from "@infiplot/engine";
+import type { SceneRequest } from "@infiplot/types";
+import { NextResponse } from "next/server";
+import { loadEngineConfig } from "@/lib/config";
+
+export const runtime = "nodejs";
+// Capped at 60 for Vercel Hobby (300 allowed on Pro). The scene pipeline is
+// Writer + CharDesigner×N + Cinematographer + Painter — happy path 9–12s; the
+// tail (cold provider, multiple new characters) can push 30–45s, so 60 is a
+// reasonable headroom on Hobby.
+export const maxDuration = 60;
+
+export async function POST(req: Request) {
+  let body: SceneRequest;
+  try {
+    body = (await req.json()) as SceneRequest;
+  } catch {
+    return NextResponse.json({ error: "Invalid JSON" }, { status: 400 });
+  }
+
+  if (!body.session) {
+    return NextResponse.json({ error: "session is required" }, { status: 400 });
+  }
+
+  try {
+    const config = loadEngineConfig();
+    const result = await requestScene(config, body);
+    return NextResponse.json(result);
+  } catch (err) {
+    const message = err instanceof Error ? err.message : "Unknown error";
+    return NextResponse.json({ error: message }, { status: 500 });
+  }
+}