feat: 第三阶段业务模块(服务产康/月嫂/进销存)

- 新增3个migration(15张表): service/nanny/inventory
- 新增15个Model + 13个Controller
- 新增55条API路由(总计212条)
- 新增3个前端API模块 + 11个管理页面
- vite build验证通过

backend/app/Models/Inventory/Inventory.php

@@ -0,0 +1,13 @@
+<?php
+namespace App\Models\Inventory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+class Inventory extends Model
+{
+    const CREATED_AT = null;
+    protected $table = 'inventories';
+    protected $fillable = ['warehouse_id','material_id','quantity','batch_no','expire_date'];
+    protected function casts(): array { return ['quantity'=>'decimal:2','expire_date'=>'date']; }
+    public function warehouse(): BelongsTo { return $this->belongsTo(Warehouse::class); }
+    public function material(): BelongsTo { return $this->belongsTo(Material::class); }
+}