feat: Complete the cycle for custom & standard Studio App builds

[ruchamahabal]

Before

App-specific builds existed & studio used to only generate these on hitting publish. But the cycle was not complete.

Current State:

• All app builds go to studio/public/app_builds/{app_name}/ regardless of standard vs custom
• That public/ folder is symlinked to sites/assets/studio/ locally, but FC doesn't symlink — it copies assets/ once during deploy
• There is no automatic rebuild when renderer changes (after bench build or bench migrate)
• The get_app_components function reads from DB (frappe.get_all("Studio Page", ...)), which doesn't work in a no-site bench build context for standard apps
• Standard apps exported to other frappe apps (e.g., frappe_app = "my_app") still write builds to studio/public/ instead of my_app/public/

After

There are 2 types of apps one can create from Studio

• Standard apps (exported to files)
• Custom apps (stored in site DB)

Completing the build cycle to handle both these categories of builds

Closes #144, Closes #97