feat(ProcessManager): add Bun availability check and improve PID file validation

- Implemented a method to check if Bun is available in the system PATH.
- Updated the startWithBun method to return an error if Bun is not found.
- Enhanced PID file parsing to validate required fields and their types.
- Cleaned up stale PID files if the process is no longer alive.

fix(SettingsRoutes): clear port cache after updating settings

- Added a call to clearPortCache after writing updated settings to ensure the application uses the latest configuration.

docs/public/architecture/search-architecture.mdx

@@ -415,7 +415,7 @@ Claude translates to appropriate API call.
 If searches fail, check worker service:
 
 ```bash
-pm2 list                    # Check status
+npm run worker:status       # Check status
 npm run worker:restart      # Restart worker
 npm run worker:logs         # View logs
 ```