feat: 支持先绑定设备后关联儿童档案

- 绑定模型新增 owner_user_id，支持 child_id 为空\n- 新增绑定后设置儿童接口 /bindings/{device_id}/child\n- 前端绑定页改为先绑设备后补充儿童\n- 补充数据库迁移脚本与 DAO 测试用例

mini-program/database/sql/003_new_tables.sql

@@ -48,7 +48,8 @@ CREATE TABLE IF NOT EXISTS parent_child_relations (
 CREATE TABLE IF NOT EXISTS device_bindings (
     id BIGINT PRIMARY KEY AUTO_INCREMENT,
     device_id VARCHAR(64) NOT NULL,
-    child_id BIGINT NOT NULL,
+    owner_user_id BIGINT NOT NULL,
+    child_id BIGINT,
     status TINYINT NOT NULL DEFAULT 1,
     bound_at DATETIME NOT NULL,
     unbound_at DATETIME,
@@ -58,6 +59,8 @@ CREATE TABLE IF NOT EXISTS device_bindings (
     UNIQUE (child_id)
 );
 
+CREATE INDEX IF NOT EXISTS idx_device_bindings_owner_user_id ON device_bindings(owner_user_id);
+
 -- device_bind_sessions table
 CREATE TABLE IF NOT EXISTS device_bind_sessions (
     id BIGINT PRIMARY KEY AUTO_INCREMENT,
@@ -81,7 +84,7 @@ CREATE TABLE IF NOT EXISTS device_bind_sessions (
 CREATE TABLE IF NOT EXISTS device_bind_history (
     id BIGINT PRIMARY KEY AUTO_INCREMENT,
     device_id VARCHAR(64) NOT NULL,
-    child_id BIGINT NOT NULL,
+    child_id BIGINT,
     bound_by_user_id BIGINT NOT NULL,
     unbound_by_user_id BIGINT,
     bind_source TINYINT NOT NULL DEFAULT 1,
@@ -211,4 +214,4 @@ CREATE TABLE IF NOT EXISTS child_location_history (
     created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
 );
 
-CREATE INDEX IF NOT EXISTS idx_child_loc_hist_child ON child_location_history(child_id, created_at);
+CREATE INDEX IF NOT EXISTS idx_child_loc_hist_child ON child_location_history(child_id, created_at);