feat: implement order relation type tracking

- Add OrderRelationType enum (UNASSIGNED, LEGACY, FIRST, CONTINUED, NEUTRAL)
- Create play_clerk_customer_relation table to track first-completed history
- Add order_relation_type column to play_order_info
- Migrate existing orders to set relation types based on completion history
- Update order services to determine relation type on creation
- Update order VOs and controllers to expose relation type in API responses
- Update clerk performance calculations to account for relation types
- Update revenue calculations to distinguish between first and continued orders
- Add comprehensive API and unit tests for order relation functionality

play-admin/src/main/resources/db/migration/V18__add_order_relation_type.sql

@@ -0,0 +1,67 @@
+CREATE TABLE play_clerk_customer_relation (
+    id VARCHAR(64) NOT NULL COMMENT '主键',
+    purchaser_by VARCHAR(64) NOT NULL COMMENT '顾客ID',
+    tenant_id VARCHAR(32) DEFAULT NULL COMMENT '租户ID',
+    accept_by VARCHAR(64) NOT NULL COMMENT '店员ID',
+    has_completed VARCHAR(1) NOT NULL DEFAULT '0' COMMENT '是否有已完成历史 0否 1是',
+    first_completed_order_id VARCHAR(64) DEFAULT NULL COMMENT '首次完成订单ID',
+    first_completed_time DATETIME DEFAULT NULL COMMENT '首次完成时间',
+    created_by VARCHAR(64) DEFAULT NULL COMMENT '创建人',
+    created_time DATETIME DEFAULT NULL COMMENT '创建时间',
+    updated_by VARCHAR(64) DEFAULT NULL COMMENT '更新人',
+    updated_time DATETIME DEFAULT NULL COMMENT '更新时间',
+    deleted TINYINT(1) NOT NULL DEFAULT '0' COMMENT '逻辑删除 1已删除 0未删除',
+    PRIMARY KEY (id),
+    UNIQUE KEY uk_clerk_customer_relation (tenant_id, purchaser_by, accept_by)
+) COMMENT '客户-店员关系(完成历史)';
+
+INSERT INTO play_clerk_customer_relation (
+    id,
+    purchaser_by,
+    tenant_id,
+    accept_by,
+    has_completed,
+    first_completed_time,
+    created_time,
+    updated_time,
+    deleted
+)
+SELECT
+    REPLACE(UUID(), '-', ''),
+    purchaser_by,
+    tenant_id,
+    accept_by,
+    '1',
+    MIN(COALESCE(order_end_time, purchaser_time)),
+    NOW(),
+    NOW(),
+    0
+FROM play_order_info
+WHERE order_status = '3'
+  AND purchaser_by IS NOT NULL
+  AND purchaser_by <> ''
+  AND tenant_id IS NOT NULL
+  AND tenant_id <> ''
+  AND accept_by IS NOT NULL
+  AND accept_by <> ''
+GROUP BY tenant_id, purchaser_by, accept_by;
+
+ALTER TABLE play_order_info
+    ADD COLUMN order_relation_type VARCHAR(32) NOT NULL DEFAULT 'LEGACY';
+
+UPDATE play_order_info o
+LEFT JOIN (
+    SELECT purchaser_by, accept_by, MIN(purchaser_time) AS first_completed_time
+    FROM play_order_info
+    WHERE order_status = '3'
+    GROUP BY purchaser_by, accept_by
+) h ON o.purchaser_by = h.purchaser_by AND o.accept_by = h.accept_by
+SET o.order_relation_type = CASE
+    WHEN o.place_type = '1' THEN 'FIRST'
+    WHEN o.accept_by IS NULL OR o.accept_by = '' THEN 'LEGACY'
+    WHEN h.first_completed_time IS NOT NULL AND o.purchaser_time > h.first_completed_time THEN 'CONTINUED'
+    ELSE 'FIRST'
+END
+WHERE o.order_relation_type IS NULL
+   OR o.order_relation_type = ''
+   OR o.order_relation_type = 'LEGACY';