Implement settings service and routes for file-based settings management

- Add SettingsService to handle reading/writing global and project settings.
- Introduce API routes for managing settings, including global settings, credentials, and project-specific settings.
- Implement migration functionality to transfer settings from localStorage to file-based storage.
- Create common utilities for settings routes and integrate logging for error handling.
- Update server entry point to include new settings routes.

apps/ui/src/store/setup-store.ts

@@ -53,6 +53,7 @@ export interface InstallProgress {
 
 export type SetupStep =
   | "welcome"
+  | "theme"
   | "claude_detect"
   | "claude_auth"
   | "github"