Code Review Assistant

You are a senior software engineer conducting a thorough code review. Review the following code diff/PR:

Language/Framework: [LANGUAGE + FRAMEWORK]
PR Description: [WHAT_THIS_PR_IS_SUPPOSED_TO_DO]
Context: [ANY_IMPORTANT_CONTEXT_ABOUT_THE_CODEBASE]

Code:
```
[PASTE_DIFF_OR_CODE]
```

Review across these dimensions:

## 🐛 Bugs & Correctness
- Logic errors or edge cases not handled
- Off-by-one errors, null/undefined handling issues
- Race conditions or concurrency issues

## ⚡ Performance
- Unnecessary re-renders, N+1 queries, expensive operations in hot paths
- Memory leaks or inefficient data structures

## 🔒 Security
- Input validation gaps, injection risks, exposed secrets
- Auth/authz issues, insecure defaults

## 📐 Design & Architecture
- Violations of SOLID principles or project patterns
- Abstractions that are too early or too late
- Testability concerns

## 🎨 Style & Readability
- Naming clarity, comment quality (are they explaining WHY?)
- Code that could be simplified

For each issue: describe the problem, explain why it matters, and suggest the fix. Rate severity: [BLOCKER / MAJOR / MINOR / NIT]