Travis builds failing across multiple PRs during Code Quality check

#### Description
It appears there is a systemic issue with the Travis CI build pipeline affecting multiple recent Pull Requests. Builds are failing during the `Build, Test & Check Code Quality` stage, which is currently blocking new contributions from being merged.

#### Observed Behavior
The build process exits immediately after the coverage summary is printed. Additionally, there is a large volume of Sass deprecation warnings regarding `@import` rules just prior to the failure.

The following PRs are currently experiencing this exact failure:
* **PR #4845** (Add purge submission queue feature)
* **PR #4843** (Add documentation for baseline submissions)
* **PR #4840** (Fix Twitter icon in web frontend)

#### Possible Causes
1. **Sass Deprecation:** The transition to Dart Sass 3.0.0 might be causing the CI to treat these warnings as fatal errors.
2. **Coverage Threshold:** The current coverage is at **87.14%**. If there is a "fail-under" requirement higher than this, it may be triggering the build failure.

#### Request for Guidance
Since I am a contributor and still learning the specific CI configurations of this repository, I am not entirely sure if my assessment of the Sass/Coverage logs is correct. Please guide me if I should provide more detailed logs or if there is anything I can do on my end to help resolve this.

Thanks for your time and help!

Start by inspecting the Travis CI configuration and the failing “Build, Test & Check Code Quality” logs for PRs #4845, #4843, and #4840. Determine whether the Sass deprecation warnings or the reported 87.14% coverage causes the exit, then verify that the affected CI stage completes successfully.

Written by the indexing model from the issue text.