Upgrade to AWS SDK v3 and latest dependencies

[Copilot]

This PR upgrades the project from AWS SDK v2 to v3 and updates all dependencies to their latest versions, addressing security vulnerabilities and improving performance.

🚀 Key Changes

AWS SDK Migration (v2 → v3)

• Replaced monolithic aws-sdk@2.1299.0 with modular v3 clients:
  • @aws-sdk/client-iam@3.864.0 for IAM operations
  • @aws-sdk/client-sts@3.864.0 for STS operations
  • @aws-sdk/client-cost-explorer@3.864.0 for Cost Explorer operations
• Updated all AWS service calls to use the new command pattern:

  // Before (v2)
  const iam = new AWS.IAM(awsConfig);
  const result = await iam.listAccountAliases().promise();
  
  // After (v3)
  const iam = new IAMClient(awsConfig);
  const result = await iam.send(new ListAccountAliasesCommand({}));

Dependency Updates

• commander@10.0.0 → 14.0.0 (latest CLI framework)
• chalk@5.2.0 → 5.6.0 (terminal styling)
• dayjs@1.11.7 → 1.11.13 (date manipulation)
• ora@6.1.2 → 8.2.0 (loading spinners)
• typescript@4.9.4 → 5.9.2 (TypeScript compiler)
• tsup@6.5.0 → 8.5.0 (bundler)
• @types/node@18.11.18 → 24.3.0 (Node.js types)

Code Improvements

• Removed AWS SDK v2 maintenance mode suppression (no longer needed)
• Enhanced error handling with proper null safety for Cost Explorer responses
• Updated configuration types for better AWS SDK v3 compatibility
• Migrated to @smithy/shared-ini-file-loader@4.0.5 (replacing deprecated package)

Security & Performance

• ✅ Fixed 2 moderate security vulnerabilities from outdated dependencies
• ✅ Zero vulnerabilities after upgrade (verified with npm audit)
• 🚀 Improved bundle size through modular AWS SDK approach
• 📦 Maintained same functionality with modern, actively maintained packages

🧪 Testing

• ✅ All TypeScript compilation passes
• ✅ Build process successful
• ✅ CLI help and version commands working
• ✅ Error handling functional (tested credential validation)
• ✅ Package contents verified for npm publishing

The CLI maintains full backward compatibility while now using the latest AWS SDK v3 architecture for better performance and security.

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