Refactor Custom project templates page to Vue
## Summary
The custom project templates page is currently using a combination of HAML partials with custom JavaScript to handle tabbing and pagination.
The current implementation is brittle (already caused two recent regressions) and difficult to maintain.
I suggest we refactor this page to use Vue components for the tabs and list.
## Improvements
Refactoring this view to Vue.js will help prevent future regressions and make it easier to maintain.
## Involved components
TBA
## Optional: Missing test coverage
I sugggest we add integration tests for this page if we don't have it by the time we pick up this issue.
issue