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/src/state/instances/model/instance.rs

@@ -88,3 +88,24 @@ pub(crate) fn playtime_to_storage(
         .into()
     })
 }
+
+/// Per-instance synchronization feature switches. Mirrors the Axolotl
+/// `InstanceSyncedOptions` shape so the sync subsystem can be ported on top of
+/// the shared `instance_sync_preferences` table.
+#[derive(Clone, Debug, Default, Serialize, Deserialize)]
+pub struct InstanceSyncedOptions {
+    #[serde(default)]
+    pub game_options: bool,
+    #[serde(default)]
+    pub command_history: bool,
+    #[serde(default)]
+    pub multiplayer_servers: bool,
+    #[serde(default)]
+    pub creative_hotbars: bool,
+    #[serde(default)]
+    pub screenshots: bool,
+    #[serde(default)]
+    pub resource_packs: bool,
+    #[serde(default)]
+    pub data_packs: bool,
+}