Adding Environment Variable for User Settings

Add server-side environment variables to configure default values for user settings.

Priority: User Custom > Server Env Var > Hardcoded Default

Steps

1. Define Environment Variable

Create packages/env/src/<domain>.ts (import path stays @/envs/<domain> — tsconfig maps to packages/env/src/* first):

import { createEnv } from '@t3-oss/env-core';
import { z } from 'zod';