fix: address code review findings

internal/cache/store.go

@@ -222,17 +222,16 @@ func (c *CacheAside) GetSearch(ctx context.Context, key *CacheKey, fetch func()
 
 	// Try cache first
 	data, err := c.store.Get(ctx, key)
-	if err == nil && data != nil {
+	if err != nil {
+		return nil, err
+	}
+	if data != nil {
 		c.metrics.RecordCacheHit("search") // cache hit
 		return data, nil
 	}
 
 	// Cache miss: fetch from backend
-	if errors.Is(err, redis.Nil) {
-		c.metrics.RecordCacheMiss("search") // record search cache miss
-	} else if err != nil {
-		return nil, err
-	}
+	c.metrics.RecordCacheMiss("search") // record search cache miss
 
 	// Fetch from backend
 	data, err = fetch()