Implement live ranking endpoint

- Add /main.php/ranking/live backed by user_live_status hi scores
- Parse live_difficulty_id from the client string payload
- Accept empty or numeric page values for the first-page request format

Signed-off-by: Sean Du <do4suki@gmail.com>

internal/handler/handler.go

@@ -24,6 +24,7 @@ import (
 	_ "honoka-chan/internal/handler/payment"
 	_ "honoka-chan/internal/handler/personalnotice"
 	_ "honoka-chan/internal/handler/profile"
+	_ "honoka-chan/internal/handler/ranking"
 	_ "honoka-chan/internal/handler/reward"
 	_ "honoka-chan/internal/handler/scenario"
 	_ "honoka-chan/internal/handler/secretbox"