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/lib/feature-flags/residential-projects.ts

@@ -0,0 +1,12 @@
+/**
+ * Server-side feature flag for the residential projects (Dự án) module.
+ *
+ * Kept in its own module (no `'use client'`) so that Server Components can
+ * import it without Next.js treating it as a client boundary export. The
+ * client-side hook lives in `@/lib/hooks/use-residential-projects-flag`.
+ */
+export function isResidentialProjectsEnabledServer(): boolean {
+  const raw = process.env['NEXT_PUBLIC_FEATURE_RESIDENTIAL_PROJECTS'];
+  if (raw == null || raw === '') return true;
+  return !(raw === '0' || raw.toLowerCase() === 'false');
+}