fix: check localStorage cache before querying relays for articles

Previously, articles always loaded from relays on browser refresh because:
- EventStore is in-memory only and doesn't persist
- localStorage cache was only checked as last resort after relay queries failed

Now we check the localStorage cache immediately after EventStore,
before querying relays. This allows instant article loading from cache
on refresh without unnecessary relay queries.

src/services/articleService.ts

@@ -34,7 +34,7 @@ function getCacheKey(naddr: string): string {
   return `${CACHE_PREFIX}${naddr}`
 }
 
-function getFromCache(naddr: string): ArticleContent | null {
+export function getFromCache(naddr: string): ArticleContent | null {
   try {
     const cacheKey = getCacheKey(naddr)
     const cached = localStorage.getItem(cacheKey)