## What does this PR do?
Replaces direct instantiation of `FeaturesRepository` with the dependency-injected version using `getFeaturesRepository()` from the DI container in the feature flags router.
**Key improvement:** The DI-ed version uses Redis caching, replacing the previous in-memory 5-minute cache implementation which was not ideal. This follows the established DI pattern in the codebase for loose coupling, better testability, and more robust caching across instances.
## Type of change
- [x] Refactor (non-breaking change that improves code quality)
## Mandatory Tasks (DO NOT REMOVE)
- [x] I have self-reviewed the code (A decent size PR without self-review might be rejected).
- [x] I have updated the developer docs in /docs if this PR makes changes that would require a [documentation change](https://cal.com/docs). N/A - no documentation changes needed.
- [x] I confirm automated tests are in place that prove my fix is effective or that my feature works.
## How should this be tested?
1. Verify feature flags functionality works as expected:
- Feature flag list endpoint should return all features
- Team feature check should work correctly
2. No environment variables needed beyond standard setup
## Checklist
- [x] My code follows the style guidelines of this project
- [x] I have checked if my changes generate no new warnings
## Human Review Checklist
- [ ] Verify `getFeaturesRepository()` returns a properly configured instance from the DI container
- [ ] Confirm the DI container properly injects the Prisma client
- [ ] Verify Redis caching is working as expected for feature flag data
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**Link to Devin run:** https://app.devin.ai/sessions/2ff6e4551c8649e4b6178b31a2195327
**Requested by:** @eunjae-lee
