fix: implement comprehensive environment variable validation system

[luisawatkins]

Problem

The application had basic environment variable validation that would cause runtime crashes with generic error messages when variables were missing or invalid.

Solution

Implemented a comprehensive environment variable validation system with:

🔍 Validation Functions

• Required Variables: Proper validation with detailed error messages
• Optional Variables: Default values with warnings instead of failures
• Numeric Validation: Type checking for numeric environment variables
• URL Validation: Proper URL format validation with parsing
• DID Validation: Decentralized Identifier format validation

Developer Tools

• Validation Script: npm run validate-env for easy validation
• Environment Template: Complete env.example with documentation
• Test Script: Test validation functions with mock data
• Health Check: Runtime environment health monitoring

Enhanced Error Handling

• Structured Logging: All validation events properly logged
• Clear Error Messages: Descriptive errors with context and solutions
• Validation Summary: Comprehensive reporting with errors, warnings, and validated variables

Files Changed

• lib/server/constants.ts - Main validation system implementation
• package.json - Added validation script command
• scripts/validate-env.mjs - Command-line validation tool
• scripts/test-env-validation.mjs - Test script for validation functions
• env.example - Complete environment variable documentation

Environment Variables Validated

Required Variables:

• SERVER_IDENTITY_PRIVATE_KEY - Server cryptographic key
• TELEGRAM_BOT_TOKEN - Telegram bot authentication
• SESSION_PASSWORD - Session security
• NEXT_PUBLIC_SERVER_DID - Server identifier (DID format)
• NEXT_PUBLIC_STORACHA_SERVICE_URL - Service URL (valid URL format)
• NEXT_PUBLIC_STORACHA_SERVICE_DID - Service identifier (DID format)
• NEXT_PUBLIC_STORACHA_RECEIPTS_URL - Receipts URL (valid URL format)
• NEXT_PUBLIC_TELEGRAM_API_ID - Telegram API ID (numeric)
• NEXT_PUBLIC_TELEGRAM_API_HASH - Telegram API hash
• NEXT_PUBLIC_POINTS_PER_BYTE - Points calculation (numeric)

Optional Variables (with defaults):

• SESSION_COOKIE_NAME - Default: 'tg-backups'
• NEXT_PUBLIC_VERSION - Default: '1.0.0'
• version - Default: '0.0.0'

Usage

Validate Environment Variables:

npm run validate-env

Runtime Health Check:

import { checkEnvironmentHealth } from '@/lib/server/constants'

if (!checkEnvironmentHealth()) {
  // Handle environment issues
}