Address review feedback: safe error handling and remove deprecated dependency

[Copilot]

Addresses actionable feedback from PR #264 review thread 3759309847.

Error handling improvement

• Use safe error message extraction in save-token route: err instanceof Error ? err.message : String(err)
• Prevents undefined access when error is not an Error instance
• Aligns with existing middleware pattern

Dependency cleanup

• Remove deprecated node-domexception package
• Native DOMException available in Node.js 20+ (project requires 20.19.0+)
• Package unused in codebase

// Before
logger.error("Ezygo verification error:", err.message);

// After
const errorMessage = err instanceof Error ? err.message : String(err);
logger.error("Ezygo verification error:", errorMessage);

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[Copilot]

Pull request overview

This PR addresses review feedback from PR #264 by implementing safe error handling and removing a deprecated dependency. The changes improve code reliability by preventing potential runtime errors when accessing error messages.

Changes:

• Implemented safe error message extraction pattern in the save-token route using instanceof Error check
• Removed deprecated node-domexception package (version 2.0.2) that was added in PR #264 but is unused

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
src/app/api/auth/save-token/route.ts	Added safe error message extraction before logging to prevent undefined access
package.json	Removed unused node-domexception dependency
package-lock.json	Removed node-domexception package entry and metadata

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