feat: 整合 Preline UI 3.x 與重寫 README 為 Docker 架構

- 新增 Preline UI 3.2.3 作為 UI 組件庫
- 更新 tailwind.config.js 整合 Preline
- 更新 app.js 初始化 Preline
- 完全重寫 README.md 以 Docker 容器化架構為核心
- 新增 Docker 常用指令大全
- 新增故障排除與生產部署指南
- 新增會員系統相關功能（會員、錢包、點數、會籍、禮物）
- 新增社交登入測試功能

app/Models/MembershipTier.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+class MembershipTier extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'name',
+        'annual_fee',
+        'discount_rate',
+        'point_multiplier',
+        'description',
+        'is_default',
+        'sort_order',
+    ];
+
+    protected $casts = [
+        'annual_fee' => 'decimal:2',
+        'discount_rate' => 'decimal:2',
+        'point_multiplier' => 'decimal:2',
+        'is_default' => 'boolean',
+        'sort_order' => 'integer',
+    ];
+
+    /**
+     * 此等級的會員紀錄
+     */
+    public function memberships(): HasMany
+    {
+        return $this->hasMany(MemberMembership::class, 'tier_id');
+    }
+
+    /**
+     * 此等級的禮品定義
+     */
+    public function giftDefinitions(): HasMany
+    {
+        return $this->hasMany(GiftDefinition::class, 'tier_id');
+    }
+
+    /**
+     * 取得預設等級
+     */
+    public static function getDefault(): ?self
+    {
+        return static::where('is_default', true)->first();
+    }
+
+    /**
+     * 是否為免費等級
+     */
+    public function getIsFreeAttribute(): bool
+    {
+        return $this->annual_fee <= 0;
+    }
+}