No magic numbers or strings without named constants

Magic numbers and strings scattered across logic files make the codebase unreadable and misconfiguration-prone. When the same timeout value appears as 3000 in five places, changing the business rule requires a grep hunt across the codebase — and missing one copy silently introduces inconsistency. ISO 25010 maintainability.analysability degrades because developers cannot distinguish a meaningful business threshold from an arbitrary implementation detail. Magic values in business rule logic are particularly dangerous because they look identical to arbitrary constants.

Consolidate logic-driving constants in a dedicated constants file and replace each inline usage with the named import:

// lib/constants.ts
export const RETRY_DELAY_MS = 3000
export const SESSION_TIMEOUT_MS = 30 * 60 * 1000  // 30 minutes
export const PASSING_SCORE_THRESHOLD = 75
export const STORAGE_KEYS = {
  USER_TOKEN: 'user_token',
  PREFERENCES: 'user_preferences',
} as const

When the business rule changes, update one place. The self-documenting multiplication 30 * 60 * 1000 is better than the magic 1800000.