Replace deprecated rand.Seed with rand.New

Updates random number generation to use the modern approach with
rand.New(rand.NewSource()) instead of the deprecated rand.Seed().

🤖 Generated with [Claude Code](https://claude.ai/code)

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

main.go

@@ -61,9 +61,9 @@ func main() {
 	defer db.Close()
 
 	// Your actual API
-    rand.Seed(time.Now().UnixNano())
+	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
 	http.HandleFunc("/randomnumber", func(w http.ResponseWriter, r *http.Request) {
-        fmt.Fprintf(w, "%d", rand.Intn(1000))
+		fmt.Fprintf(w, "%d", rng.Intn(1000))
 	})
 
 	http.HandleFunc("/slowtest", func(w http.ResponseWriter, r *http.Request) {