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>

lib/config.ts

@@ -0,0 +1,45 @@
+import type { EngineConfig, TtsConfig } from "@infiplot/types";
+
+function readVar(name: string): string {
+  const v = process.env[name];
+  if (!v) throw new Error(`Missing required environment variable: ${name}`);
+  return v;
+}
+
+function readOptionalVar(name: string): string | undefined {
+  const v = process.env[name];
+  return v && v.length > 0 ? v : undefined;
+}
+
+function loadTtsConfig(): TtsConfig | undefined {
+  const baseUrl = readOptionalVar("TTS_BASE_URL");
+  const apiKey = readOptionalVar("TTS_API_KEY");
+  const speechModel = readOptionalVar("TTS_SPEECH_MODEL");
+
+  // Missing any → TTS disabled (game runs silently).
+  if (!baseUrl || !apiKey || !speechModel) return undefined;
+
+  return { baseUrl, apiKey, speechModel };
+}
+
+export function loadEngineConfig(): EngineConfig {
+  return {
+    text: {
+      baseUrl: readVar("TEXT_BASE_URL"),
+      apiKey: readVar("TEXT_API_KEY"),
+      model: readVar("TEXT_MODEL"),
+    },
+    image: {
+      baseUrl: readVar("IMAGE_BASE_URL"),
+      apiKey: readVar("IMAGE_API_KEY"),
+      model: readVar("IMAGE_MODEL"),
+    },
+    vision: {
+      baseUrl: readVar("VISION_BASE_URL"),
+      apiKey: readVar("VISION_API_KEY"),
+      model: readVar("VISION_MODEL"),
+    },
+    tts: loadTtsConfig(),
+    mockImage: readOptionalVar("MOCK_IMAGE") === "true",
+  };
+}