fix: separate client and server utilities to fix build error

Split lib/utils.ts into:
- lib/utils.ts: Client-safe utilities only (no Node.js imports)
- lib/project-utils.ts: Server-only utilities with Node.js imports

This fixes the Next.js build error where client components were importing
modules that contained Node.js dependencies (fs, path).

All tests pass and build succeeds.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/projects/route.ts

@@ -1,7 +1,7 @@
 // app/api/projects/route.ts
 import { NextResponse } from 'next/server';
 import { getProjects } from '@/lib/fs-utils';
-import { getProjectDisplayName } from '@/lib/utils';
+import { getProjectDisplayName } from '@/lib/project-utils';
 
 export async function GET() {
   try {