feat: add read-only Social Accounts API

Add GET /api/accounts (list with optional ?network= and ?type= filters) and
GET /api/accounts/{socialAccount} (show) endpoints. Include plain-text password
field for AI agent consumption.

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

routes/api.php

@@ -1,7 +1,11 @@
 <?php
 
 use App\Http\Controllers\Api\SiteController;
+use App\Http\Controllers\Api\SocialAccountController;
 use Illuminate\Support\Facades\Route;
 
 Route::get('/sites', [SiteController::class, 'index']);
 Route::get('/sites/{site}', [SiteController::class, 'show']);
+
+Route::get('/accounts', [SocialAccountController::class, 'index']);
+Route::get('/accounts/{socialAccount}', [SocialAccountController::class, 'show']);