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/AccountTransaction.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace App\Models\Finance;
+
+use App\Models\Crm\Customer;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class AccountTransaction extends Model
+{
+    const UPDATED_AT = null;
+
+    protected $fillable = [
+        'store_id', 'customer_account_id', 'customer_id', 'type',
+        'amount', 'balance_after', 'related_type', 'related_id',
+        'description', 'operator_id',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'type' => 'integer',
+            'amount' => 'decimal:2',
+            'balance_after' => 'decimal:2',
+        ];
+    }
+
+    public function account(): BelongsTo
+    {
+        return $this->belongsTo(CustomerAccount::class, 'customer_account_id');
+    }
+
+    public function customer(): BelongsTo
+    {
+        return $this->belongsTo(Customer::class);
+    }
+}