sync: add AI review pipeline, parallel skill-files fetch, Redis cache improvements

- feat(review): add skill_reviews table, review API endpoints (pending/submit/stats), admin auth
- perf: parallel file fetching in skill-files API (was sequential → timeout)
- fix: handle Date serialization from Redis cache
- fix: align curation batch scripts with current browseReadyFilter

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

apps/web/lib/cache.ts

@@ -168,6 +168,7 @@ export const cacheKeys = {
   skill: (id: string) => `skill:${id.replace(/\//g, ':')}`,
   skillView: (skillId: string, ip: string) => `view:${skillId.replace(/\//g, ':')}:${ip}`,
   skillDownload: (skillId: string, ip: string) => `download:${skillId.replace(/\//g, ':')}:${ip}`,
+  reviewStats: () => 'review:stats',
 };
 
 // TTL values in seconds
@@ -184,6 +185,7 @@ export const cacheTTL = {
   pageCount: 60 * 60,       // 1 hour
   view: 60 * 60,            // 1 hour - same IP can only count as 1 view per hour
   download: 5 * 60,         // 5 minutes - same IP can only count as 1 download per 5 min
+  reviewStats: 60,          // 1 minute - admin review stats
 };
 
 /**