Code Review Bench PR #26061 - fix: enable DI for FeatureOptInService

[tomerqodo]

Code Review Bench PR calcom#26061

Original PR Title: fix: enable DI for FeatureOptInService
Original PR Description: ## What does this PR do?

This PR adds DI support for FeatureOptInService and FeaturesRepository.

But we're still using FeaturesRepository directly across the project, and I will fix it in a separate PR.

Updates since last revision

• Renamed FeatureOptInServiceInterface.ts to IFeatureOptInService.ts to follow the codebase convention of using I prefix for interface files
• Renamed the interface from FeatureOptInServiceInterface to IFeatureOptInService
• Updated all references to use the new naming convention

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• N/A - I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

1. Run type checks: yarn type-check:ci --force
2. Run tests: TZ=UTC yarn test
3. Verify the DI containers correctly resolve FeatureOptInService and FeaturesRepository

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Summary by cubic

Enables DI for FeatureOptInService and FeaturesRepository across the app. Replaces direct instantiation and Prisma usage with moduleLoader-based containers and updates router/tests to resolve the service via DI.

• Refactors
  • Added DI modules/containers and helpers for FeatureOptInService and FeaturesRepository; introduced feature-specific DI tokens and merged them into DI_TOKENS.
  • Replaced the deprecated Features module with FeaturesRepository module and updated related imports.
  • Added IFeatureOptInService and implemented it in the service.
  • Updated TRPC viewer.featureOptIn router and integration tests to use DI.

^{Written for commit 259569f. Summary will update on new commits.}

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Link to Devin run: https://app.devin.ai/sessions/de393c9ea2b8412587a8c4ca8cb2631d
Requested by: @eunjae-lee (eunjae@cal.com)
Original PR URL: calcom#26061