feat(payment): integrate Polar.sh payment provider with checkout flow

- Build PolarProvider from scratch with proper HTTP API integration
  - Add encrypted configuration loading from payment_providers table via model
  - Implement sandbox/live environment switching with proper credential handling
  - Fix product creation API structure for Polar.sh requirements
  - Add comprehensive error handling and logging throughout checkout flow
  - Fix PaymentController checkout URL handling to support Polar's checkout_url response
  - Add debug logging for troubleshooting checkout session creation
  - Support both regular and trial checkout flows for Polar payments

routes/web.php

@@ -1,6 +1,28 @@
 <?php
 
 use App\Http\Controllers\AppController;
+
+// DEBUG: Test route to check PolarProvider
+Route::get('/debug-polar', function () {
+    try {
+        $provider = new \App\Services\Payments\Providers\PolarProvider;
+
+        return response()->json([
+            'status' => 'success',
+            'provider_class' => get_class($provider),
+            'is_active' => $provider->isActive(),
+            'config' => $provider->getConfiguration(),
+            'sandbox' => $provider->config['sandbox'] ?? 'unknown',
+            'timestamp' => '2025-12-04-17-15-00',
+        ]);
+    } catch (\Exception $e) {
+        return response()->json([
+            'status' => 'error',
+            'message' => $e->getMessage(),
+            'trace' => $e->getTraceAsString(),
+        ]);
+    }
+});
 use App\Http\Controllers\ImpersonationController;
 use App\Http\Controllers\WebhookController;
 use App\Http\Middleware\CheckPageSlug;