feat: add Weeztix OAuth, coupon codes, and Mailwizz mapping

Implement Weeztix integration per documentation: database config and
subscriber coupon_code, OAuth redirect/callback, admin setup UI with
company/coupon selection via AJAX, synchronous coupon creation on public
subscribe with duplicate and rate-limit handling, Mailwizz field mapping
for coupon codes, subscriber table and CSV export, and connection hint
on the pages list.

Made-with: Cursor

app/Models/WeeztixConfig.php

@@ -0,0 +1,64 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class WeeztixConfig extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'preregistration_page_id',
+        'client_id',
+        'client_secret',
+        'redirect_uri',
+        'access_token',
+        'refresh_token',
+        'token_expires_at',
+        'refresh_token_expires_at',
+        'company_guid',
+        'company_name',
+        'coupon_guid',
+        'coupon_name',
+        'code_prefix',
+        'usage_count',
+        'is_connected',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'client_id' => 'encrypted',
+            'client_secret' => 'encrypted',
+            'access_token' => 'encrypted',
+            'refresh_token' => 'encrypted',
+            'token_expires_at' => 'datetime',
+            'refresh_token_expires_at' => 'datetime',
+            'is_connected' => 'boolean',
+        ];
+    }
+
+    public function preregistrationPage(): BelongsTo
+    {
+        return $this->belongsTo(PreregistrationPage::class);
+    }
+
+    public function isTokenExpired(): bool
+    {
+        return ! $this->token_expires_at || $this->token_expires_at->isPast();
+    }
+
+    public function isRefreshTokenExpired(): bool
+    {
+        if ($this->refresh_token_expires_at === null) {
+            return false;
+        }
+
+        return $this->refresh_token_expires_at->isPast();
+    }
+}