[FR] Improve initial login experience during permission syncing (repo sync delay) #817

Feature Description

When a new user logs in to Sourcebot and permission syncing is enabled, they currently see an empty repo list, which slowly fills in as repositories finish syncing in the background. This experience can be confusing or discouraging, especially when syncing a large number of repos (e.g. 1000+), as it may take hours for all repos to appear.

Current Problem:

• After signing up/logging in for the first time, the user sees "no repos" for a significant amount of time until syncing finishes.
• This initial experience is critical for capturing new user interest and engagement, but asking users to wait hours for repo availability is a poor onboarding experience.

Expected Improvements:

• Provide visual feedback or messaging during the syncing process to set expectations (e.g., display a progress bar, count of repos synced so far, estimate of time, "Syncing your repos..." notice, etc.)
• Consider pre-fetching or prioritizing certain repositories so that the user is quickly presented with meaningful data (e.g., most recently active/starred/pinned repos) while the full sync continues in the background.

User Story

• As a new user, I want to understand that my repositories are syncing and see progress, so that I am not confused by an empty screen during my first login experience.