Add create project functionality

[gergesh]

My attempt at closing my own issue #5581

Summary

• Added "Create project" button to home page (both in header and empty state)
• Added POST /project API endpoint for project creation which initializes git repo with blank commit if needed

[gergesh]

I force-pushed it to resolve the conflicts with latest dev Here's what it looks like btw In the homepage: In the sidebar:

[gergesh]

And the dialog