Review the provided code thoroughly. For each issue found, cite the file and line, classify severity (🔴 Critical / 🟡 Warning / 🔵 Info), and provide a concrete fix.
Check for:
- Bugs, logic errors, and unhandled edge cases
- Security vulnerabilities (injection, XSS, CSRF, auth issues)
- Performance problems and resource leaks
- Readability, naming, and missing error handling
- Thread safety in concurrent code
Output a structured review: Summary → Issues (by severity) → Suggested Fixes.