feat: add HOSTNAME and VITE_HOSTNAME support for improved server URL configuration

- Introduced `HOSTNAME` environment variable for user-facing URLs, defaulting to localhost.
- Updated server and client code to utilize `HOSTNAME` for constructing URLs instead of hardcoded localhost.
- Enhanced documentation in CLAUDE.md to reflect new configuration options.
- Added `VITE_HOSTNAME` for frontend API URLs, ensuring consistent hostname usage across the application.

These changes improve flexibility in server configuration and enhance the user experience by providing accurate URLs.

apps/ui/src/components/views/board-view/worktree-panel/hooks/use-dev-server-logs.ts

@@ -93,7 +93,7 @@ export function useDevServerLogs({ worktreePath, autoSubscribe = true }: UseDevS
           isRunning: true,
           isLoading: false,
           port: result.result!.port,
-          url: `http://localhost:${result.result!.port}`,
+          url: result.result!.url,
           startedAt: result.result!.startedAt,
           error: null,
         }));