feat(sync): 跨实例同步第1轮——同步功能表、InstanceSyncedOptions 类型与实例元数据字段

- 新增 4 个 migration：同步功能表/instance_servers 扩展/synced_pack_selection/禁用发现选项

- 新增 InstanceSyncedOptions 类型（per-instance 同步开关）

- InstanceMetadata 增加 synced_options 字段并在 3 个查询点填充

- instance_rows 新增 get_instance_synced_options

- 前端 GameInstance 增加 synced_options 类型

packages/app-lib/migrations/20261003000300_disable-discovered-game-options.sql

@@ -0,0 +1,5 @@
+-- Discovered options are catalogued for review, but must not be synced until
+-- the user explicitly enables them.
+UPDATE synced_game_option_preferences
+SET enabled = 0
+WHERE source = 'discovery_default' AND enabled = 1;