feat: 第四阶段财务与人事薪资模块

- 新增2个migration(11张表): finance(6表)/hr(5表)
- 新增11个Model + 11个Controller
- 新增50条API路由(总计262条)
- 新增2个前端API模块 + 10个管理页面
- 迁移运行通过, vite build验证通过

backend/app/Models/Finance/PrepaidCard.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Models\Finance;
+
+use App\Traits\BelongsToStore;
+use Illuminate\Database\Eloquent\Model;
+
+class PrepaidCard extends Model
+{
+    use BelongsToStore;
+
+    protected $fillable = [
+        'store_id', 'name', 'face_value', 'sell_price',
+        'discount_rate', 'validity_days', 'status', 'sort',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'face_value' => 'decimal:2',
+            'sell_price' => 'decimal:2',
+            'discount_rate' => 'decimal:2',
+            'validity_days' => 'integer',
+            'status' => 'integer',
+            'sort' => 'integer',
+        ];
+    }
+}