Code Architecture Review

Review the following codebase architecture for a {{projectType}} application.

**Tech stack:** {{techStack}}
**Scale:** {{scaleRequirements}}
**Team size:** {{teamSize}} engineers

I'll provide the key files. For each architectural concern, reference the specific file and line where the issue exists.

Review for:
1. **Separation of concerns** — Are responsibilities cleanly divided? Any God objects or modules doing too much?
2. **Scalability bottlenecks** — What breaks first at 10x current load?
3. **Error handling gaps** — Where can failures cascade or go unhandled?
4. **Testing friction** — What's hard to test due to tight coupling or hidden dependencies?
5. **Security surface** — Auth bypasses, injection points, data exposure risks

For each issue found, provide:
- Severity: critical / high / medium / low
- The specific anti-pattern or violation
- A concrete fix with code example

<codebase>
{{codebaseFiles}}
</codebase>