fix(api): remove "type": "module" conflicting with CommonJS build output

The NestJS tsconfig compiles to CommonJS (module: "CommonJS") but
package.json had "type": "module", causing Node.js v24 to treat the
CJS output as ESM and fail with "exports is not defined in ES module
scope" at startup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/package.json

@@ -2,7 +2,6 @@
   "name": "@mosaic/api",
   "version": "0.0.1",
   "private": true,
-  "type": "module",
   "scripts": {
     "build": "nest build",
     "dev": "nest start --watch",