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/20261003000100_linked-server-project-sync-source.sql

@@ -0,0 +1,27 @@
+-- Axolotl stores managed server-project entries alongside the local additions
+-- that are composed with the launcher-wide multiplayer server list. Extend
+-- the original sync table constraint without changing the already-applied
+-- instance-sync migration.
+CREATE TABLE instance_servers_new (
+	instance_id TEXT NOT NULL,
+	id TEXT NOT NULL,
+	source TEXT NOT NULL CHECK (
+		source IN ('modpack', 'linked_server_project', 'local_desynced')
+	),
+	excluded_synced_server_id TEXT,
+	nbt BLOB NOT NULL,
+	position INTEGER NOT NULL CHECK (position >= 0),
+	PRIMARY KEY (instance_id, id),
+	UNIQUE (instance_id, position),
+	FOREIGN KEY (instance_id) REFERENCES instances (id) ON DELETE CASCADE,
+	FOREIGN KEY (excluded_synced_server_id)
+		REFERENCES synced_servers (id) ON DELETE SET NULL
+);
+
+INSERT INTO instance_servers_new
+	(instance_id, id, source, excluded_synced_server_id, nbt, position)
+SELECT instance_id, id, source, excluded_synced_server_id, nbt, position
+FROM instance_servers;
+
+DROP TABLE instance_servers;
+ALTER TABLE instance_servers_new RENAME TO instance_servers;