feat: add SocialAccount model, migration, and factory

Implement SocialAccount model with enum fields for network and type,
along with migration and factory. Includes NETWORKS and TYPES constants
for dropdown usage in Livewire forms and validation.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/Models/SocialAccount.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class SocialAccount extends Model
+{
+    use HasFactory;
+
+    public const NETWORKS = [
+        'twitter', 'instagram', 'facebook', 'reddit',
+        'tiktok', 'linkedin', 'youtube', 'other',
+    ];
+
+    public const TYPES = ['post', 'comment', 'like'];
+
+    protected $fillable = [
+        'network',
+        'username',
+        'email',
+        'password',
+        'type',
+    ];
+}