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/Nanny/Nanny.php

@@ -0,0 +1,13 @@
+<?php
+namespace App\Models\Nanny;
+use App\Traits\BelongsToStore;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+class Nanny extends Model
+{
+    use BelongsToStore;
+    protected $fillable = ['store_id','name','phone','id_card','avatar','level','skills','experience_years','health_cert','cooperation_type','base_salary','introduction','status'];
+    protected function casts(): array { return ['level'=>'integer','skills'=>'array','experience_years'=>'integer','cooperation_type'=>'integer','base_salary'=>'decimal:2','status'=>'integer']; }
+    public function orders(): HasMany { return $this->hasMany(NannyOrder::class); }
+    public function schedules(): HasMany { return $this->hasMany(NannySchedule::class); }
+}