Replace dotenv with zod for type-safe env validation

[ReverseGem7]

• Remove dotenv dependency and deprecated env.d.ts type declarations
• Implement Zod schema for runtime validation and type inference
• Add global type augmentation for process.env
• Update deploy scripts to use --env-file flag

Example output:

❌ Invalid environment variables: {
  _errors: [],
  DISCORD_TOKEN: {
    _errors: [ "Required" ],
  },
  BOT_ENDPOINT_API_KEY: {
    _errors: [ "Required" ],
  },
  EXPERIENCE_ENDPOINT_API_SECRET: {
    _errors: [ "Required" ],
  },
  BOT_ERROR_WEBHOOK_URL: {
    _errors: [ "Required" ],
  },
  REDIS_USERNAME: {
    _errors: [ "Required" ],
  },
  REDIS_PASSWORD: {
    _errors: [ "Required" ],
  },
  REDIS_HOST: {
    _errors: [ "Required" ],
  },
}