sync(theme-2): 同步 main 最新 API/Admin 与玩家端逻辑

从 main 同步站内信手动发送、媒体库选择、列表子路由重构等 API/Admin 改动；玩家端仅合并 ADMIN_CUSTOM 富文本、消息预览与充值截图压缩逻辑，保留 theme-2 样式。

apps/api/prisma/migrations/20260622140000_player_message_broadcast_translations/migration.sql

@@ -0,0 +1,9 @@
+-- AlterTable
+ALTER TABLE "player_message_broadcasts" ADD COLUMN "translations" JSONB;
+
+-- Backfill existing rows as English content
+UPDATE "player_message_broadcasts"
+SET "translations" = jsonb_build_object(
+  'en-US', jsonb_build_object('title', "title", 'body', "body")
+)
+WHERE "translations" IS NULL;