Remove unused code and cleanup routes after dashboard/projects refactor

What does this MR do and why?

Related to #523698 (closed)

In Migrate Your Work > Projects list to Vue and mo... (&13066 - closed) we migrated Your work -> Projects from HAML/vanilla JS to Vue with GraphQL data source. This MR cleans up some routes and removes some old HAML templates and unused JavaScript.

References

Screenshots or screen recordings

No visual changes, video demonstrates all still works

Screen_Recording_2025-04-03_at_12.36.52_PM

How to set up and validate locally

1. Go to /dashboard/projects all functionality should work
2. Go to /dashboard/projects/removed, it should redirect to /dashboard/projects/inactive

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.