Set up a linter #2096
Description
Objective: Add the official Flutter linter to the Campus Mobile project.
Reasoning: This will help improve existing code quality and enforce future code quality, especially for Campus Activation Project tasks.
Note: SonarQube/SonarLint was suggested by Alex as a potential alternative. However, first-party support for Flutter/Dart is currently unstable there. It is unclear how soon it will stabilize. This could be looked into again in the future for performing automated code quality checks.