feat: 打通采购申请与入库的按单入库链路

后端变更:
- PurchaseRequest 新增 base_id 硬关联 MaterialBase，StockBuy 新增 request_id 关联采购单
- handle_inbound 支持 request_id 入参，入库后自动反写采购单状态为已完成
- 新增 get_approved_requests 接口，返回已审批未入库采购单列表（含物料信息+历史数据回退匹配）
- create_purchase_request 新增 name+spec_model 自动匹配 MaterialBase
- 新增 SQL 和 Alembic 数据库迁移脚本

前端变更:
- 入库表单新增"从采购单导入"弹窗，支持搜索/选中已审批采购单并一键填充物料和商务信息
- 单价/总价交叉推算，缺项自动补全
- 选中行蓝色高亮+点击整行选中，行级交互优化

inventory-backend/migrations_add_purchase_stockbuy_link.sql

@@ -0,0 +1,93 @@
+-- ============================================================
+-- migrations_add_purchase_stockbuy_link.sql
+-- 打通「采购申请」与「采购入库」的按单入库链路
+--
+-- 变更内容:
+--   1. purchase_request 表新增 base_id 列（FK → material_base.id）
+--   2. stock_buy 表新增 request_id 列（FK → purchase_request.id）
+--
+-- 执行方式（任选一种）:
+--   psql -h <host> -U postgres -d inventory_system -f migrations_add_purchase_stockbuy_link.sql
+--   或在 pgAdmin / Navicat / DBeaver 中打开执行
+-- ============================================================
+
+BEGIN;
+
+-- ============================================================
+-- 1. purchase_request 新增 base_id
+--    硬关联基础物料表，使采购申请能精确锁定物料
+-- ============================================================
+ALTER TABLE purchase_request
+    ADD COLUMN IF NOT EXISTS base_id INTEGER;
+
+-- 添加外键约束（如果列已存在但无约束，会补充）
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM information_schema.table_constraints
+        WHERE constraint_name = 'fk_purchase_request_base_id'
+          AND table_name = 'purchase_request'
+    ) THEN
+        ALTER TABLE purchase_request
+            ADD CONSTRAINT fk_purchase_request_base_id
+            FOREIGN KEY (base_id) REFERENCES material_base(id)
+            ON DELETE SET NULL;
+    END IF;
+END;
+$$;
+
+-- 为 base_id 添加索引（支持按物料筛选采购申请）
+CREATE INDEX IF NOT EXISTS ix_purchase_request_base_id
+    ON purchase_request (base_id);
+
+COMMENT ON COLUMN purchase_request.base_id IS '关联基础物料ID';
+
+
+-- ============================================================
+-- 2. stock_buy 新增 request_id
+--    关联采购申请单，使入库记录可追溯到来源采购单
+-- ============================================================
+ALTER TABLE stock_buy
+    ADD COLUMN IF NOT EXISTS request_id INTEGER;
+
+-- 添加外键约束
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM information_schema.table_constraints
+        WHERE constraint_name = 'fk_stock_buy_request_id'
+          AND table_name = 'stock_buy'
+    ) THEN
+        ALTER TABLE stock_buy
+            ADD CONSTRAINT fk_stock_buy_request_id
+            FOREIGN KEY (request_id) REFERENCES purchase_request(id)
+            ON DELETE SET NULL;
+    END IF;
+END;
+$$;
+
+-- 为 request_id 添加索引（支持"按单查入库"的追溯查询）
+CREATE INDEX IF NOT EXISTS ix_stock_buy_request_id
+    ON stock_buy (request_id);
+
+COMMENT ON COLUMN stock_buy.request_id IS '关联采购申请单ID';
+
+
+-- ============================================================
+-- 3. 验证结果
+-- ============================================================
+SELECT
+    column_name,
+    data_type,
+    is_nullable,
+    pg_catalog.col_description(
+        (SELECT c.oid FROM pg_catalog.pg_class c
+         WHERE c.relname = table_name),
+        ordinal_position
+    ) AS comment
+FROM information_schema.columns
+WHERE table_name IN ('purchase_request', 'stock_buy')
+  AND column_name IN ('base_id', 'request_id')
+ORDER BY table_name, column_name;
+
+COMMIT;