fix(du-an): stop detail page crash from thin backend payload + client/server flag boundary

- Split `isResidentialProjectsEnabledServer` out of the `'use client'`
  hook file into `lib/feature-flags/residential-projects.ts` so Server
  Components can import it without Next.js treating it as a client ref.
- Detail endpoint preserves `media` via new `shapeProjectDetail`
  instead of stripping it in `shapeProject`.
- `fetchProjectBySlug` now normalizes the response: fills missing
  arrays (media, blocks, amenities, priceRanges, priceHistory,
  neighborhoodScores, pois, documents) with `[]`, remaps
  `developer.logo` → `logoUrl`, defaults `totalProjects` to 0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/[locale]/(public)/du-an/[slug]/page.tsx

@@ -2,7 +2,7 @@ import type { Metadata } from 'next';
 import { notFound } from 'next/navigation';
 import { DuAnDetailClient } from '@/components/du-an/du-an-detail-client';
 import { fetchProjectBySlug } from '@/lib/du-an-server';
-import { isResidentialProjectsEnabledServer } from '@/lib/hooks/use-residential-projects-flag';
+import { isResidentialProjectsEnabledServer } from '@/lib/feature-flags/residential-projects';
 
 interface PageProps {
   params: Promise<{ slug: string; locale: string }>;