feat: 实现客户端换货系统（client-exchange-system）

新增完整换货生命周期管理：后台发起 → 客户端填收货信息 → 后台发货 → 确认完成（含可选全量迁移） → 旧资产转新再销售

后台接口（7个）：
- POST /api/admin/exchanges（发起换货）
- GET /api/admin/exchanges（换货列表）
- GET /api/admin/exchanges/:id（换货详情）
- POST /api/admin/exchanges/:id/ship（发货）
- POST /api/admin/exchanges/:id/complete（确认完成+可选迁移）
- POST /api/admin/exchanges/:id/cancel（取消）
- POST /api/admin/exchanges/:id/renew（旧资产转新）

客户端接口（2个）：
- GET /api/c/v1/exchange/pending（查询换货通知）
- POST /api/c/v1/exchange/:id/shipping-info（填写收货信息）

核心能力：
- ExchangeOrder 模型与状态机（1待填写→2待发货→3已发货→4已完成，1/2可取消→5）
- 全量迁移事务（11张表：钱包、套餐、标签、客户绑定等）
- 旧资产转新（generation+1、状态重置、新钱包、历史隔离）
- 旧 CardReplacementRecord 表改名为 legacy，is_replaced 过滤改为查新表
- 数据库迁移：000085 新建 tb_exchange_order，000086 旧表改名

migrations/000085_add_exchange_order.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS tb_exchange_order;

migrations/000085_add_exchange_order.up.sql

@@ -0,0 +1,75 @@
+CREATE TABLE IF NOT EXISTS tb_exchange_order (
+    id BIGSERIAL PRIMARY KEY,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    deleted_at TIMESTAMPTZ,
+    creator BIGINT NOT NULL DEFAULT 0,
+    updater BIGINT NOT NULL DEFAULT 0,
+
+    exchange_no VARCHAR(50) NOT NULL,
+
+    old_asset_type VARCHAR(20) NOT NULL,
+    old_asset_id BIGINT NOT NULL,
+    old_asset_identifier VARCHAR(100) NOT NULL,
+
+    new_asset_type VARCHAR(20) DEFAULT '',
+    new_asset_id BIGINT,
+    new_asset_identifier VARCHAR(100) DEFAULT '',
+
+    recipient_name VARCHAR(50) DEFAULT '',
+    recipient_phone VARCHAR(20) DEFAULT '',
+    recipient_address TEXT DEFAULT '',
+
+    express_company VARCHAR(100) DEFAULT '',
+    express_no VARCHAR(100) DEFAULT '',
+
+    migrate_data BOOLEAN NOT NULL DEFAULT FALSE,
+    migration_completed BOOLEAN NOT NULL DEFAULT FALSE,
+    migration_balance BIGINT NOT NULL DEFAULT 0,
+
+    exchange_reason VARCHAR(100) NOT NULL,
+    remark TEXT,
+    status INT NOT NULL DEFAULT 1,
+
+    shop_id BIGINT
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_exchange_order_no
+    ON tb_exchange_order (exchange_no)
+    WHERE deleted_at IS NULL;
+
+CREATE INDEX IF NOT EXISTS idx_exchange_order_old_asset
+    ON tb_exchange_order (old_asset_type, old_asset_id)
+    WHERE deleted_at IS NULL;
+
+CREATE INDEX IF NOT EXISTS idx_exchange_order_status
+    ON tb_exchange_order (status)
+    WHERE deleted_at IS NULL;
+
+CREATE INDEX IF NOT EXISTS idx_exchange_order_shop_id
+    ON tb_exchange_order (shop_id)
+    WHERE deleted_at IS NULL;
+
+CREATE INDEX IF NOT EXISTS idx_exchange_order_created_at
+    ON tb_exchange_order (created_at DESC);
+
+COMMENT ON TABLE tb_exchange_order IS '换货订单表';
+COMMENT ON COLUMN tb_exchange_order.exchange_no IS '换货单号(EXC+日期+随机数)';
+COMMENT ON COLUMN tb_exchange_order.old_asset_type IS '旧资产类型(iot_card/device)';
+COMMENT ON COLUMN tb_exchange_order.old_asset_id IS '旧资产ID';
+COMMENT ON COLUMN tb_exchange_order.old_asset_identifier IS '旧资产标识符(ICCID/虚拟号)';
+COMMENT ON COLUMN tb_exchange_order.new_asset_type IS '新资产类型(iot_card/device)';
+COMMENT ON COLUMN tb_exchange_order.new_asset_id IS '新资产ID';
+COMMENT ON COLUMN tb_exchange_order.new_asset_identifier IS '新资产标识符(ICCID/虚拟号)';
+COMMENT ON COLUMN tb_exchange_order.recipient_name IS '收件人姓名';
+COMMENT ON COLUMN tb_exchange_order.recipient_phone IS '收件人电话';
+COMMENT ON COLUMN tb_exchange_order.recipient_address IS '收货地址';
+COMMENT ON COLUMN tb_exchange_order.express_company IS '快递公司';
+COMMENT ON COLUMN tb_exchange_order.express_no IS '快递单号';
+COMMENT ON COLUMN tb_exchange_order.migrate_data IS '是否执行全量迁移';
+COMMENT ON COLUMN tb_exchange_order.migration_completed IS '迁移是否已完成';
+COMMENT ON COLUMN tb_exchange_order.migration_balance IS '迁移转移金额(分)';
+COMMENT ON COLUMN tb_exchange_order.exchange_reason IS '换货原因';
+COMMENT ON COLUMN tb_exchange_order.remark IS '备注';
+COMMENT ON COLUMN tb_exchange_order.status IS '换货状态 1-待填写信息 2-待发货 3-已发货待确认 4-已完成 5-已取消';
+COMMENT ON COLUMN tb_exchange_order.shop_id IS '所属店铺ID';

migrations/000086_rename_card_replacement_to_legacy.down.sql

@@ -0,0 +1 @@
+ALTER TABLE tb_card_replacement_record_legacy RENAME TO tb_card_replacement_record;

migrations/000086_rename_card_replacement_to_legacy.up.sql

@@ -0,0 +1 @@
+ALTER TABLE tb_card_replacement_record RENAME TO tb_card_replacement_record_legacy;