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/20260622120000_player_message_broadcasts/migration.sql

@@ -0,0 +1,27 @@
+-- CreateTable
+CREATE TABLE "player_message_broadcasts" (
+    "id" BIGSERIAL NOT NULL,
+    "title" VARCHAR(256) NOT NULL,
+    "body" TEXT NOT NULL,
+    "target_type" VARCHAR(16) NOT NULL,
+    "target_user_id" BIGINT,
+    "target_username" VARCHAR(64),
+    "recipient_count" INTEGER NOT NULL DEFAULT 0,
+    "created_by_id" BIGINT,
+    "created_by_username" VARCHAR(64),
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "player_message_broadcasts_pkey" PRIMARY KEY ("id")
+);
+
+-- AlterTable
+ALTER TABLE "player_messages" ADD COLUMN "broadcast_id" BIGINT;
+
+-- CreateIndex
+CREATE INDEX "player_message_broadcasts_created_at_idx" ON "player_message_broadcasts"("created_at" DESC);
+
+-- CreateIndex
+CREATE INDEX "player_messages_broadcast_id_idx" ON "player_messages"("broadcast_id");
+
+-- AddForeignKey
+ALTER TABLE "player_messages" ADD CONSTRAINT "player_messages_broadcast_id_fkey" FOREIGN KEY ("broadcast_id") REFERENCES "player_message_broadcasts"("id") ON DELETE CASCADE ON UPDATE CASCADE;