Custom project icons not displayed in workspace sidebar — GitHub icon fallback #187

Bug

Custom project icons set in Appearance settings are not rendered in the workspace sidebar.
A GitHub octocat icon is displayed for all projects, even those with no git remote.

Expected

Custom icons should appear in the sidebar next to each project name.

Diagnostic

• projects table has valid icon_path for both projects
• Image files exist in ~/Library/Application Support/21st-desktop/project-icons/
  (JPEG 17KB and PNG 2.5MB)
• git_provider, git_remote_url, git_owner, git_repo are all NULL for both projects
• Despite no git association, the GitHub icon is used as default fallback

Steps to reproduce

1. Open Settings → Appearance → enable project icons
2. Set a custom icon for each project
3. Go back to the workspace/sidebar view
4. → All projects show the GitHub octocat icon instead of the custom ones

Environment

• 1Code v0.0.84
• macOS Sequoia (Darwin 25.3.0)
• 2 projects, neither linked to a git remote

Suggested fix

The sidebar should read icon_path from the project record.
The GitHub icon should only appear when git_provider = 'github' and no custom icon is set.