feat: implement comprehensive multi-provider payment processing system

- Add unified payment provider architecture with contract-based design
  - Implement 6 payment providers: Stripe, Lemon Squeezy, Polar, Oxapay, Crypto, Activation Keys
  - Create subscription management with lifecycle handling (create, cancel, pause, resume, update)
  - Add coupon system with usage tracking and trial extensions
  - Build Filament admin resources for payment providers, subscriptions, coupons, and trials
  - Implement payment orchestration service with provider registry and configuration management
  - Add comprehensive payment logging and webhook handling for all providers
  - Create customer analytics dashboard with revenue, churn, and lifetime value metrics
  - Add subscription migration service for provider switching
  - Include extensive test coverage for all payment functionality

routes/web.php

@@ -157,6 +157,9 @@ Route::middleware(['auth'])->group(function (): void {
 
 Route::post('/webhook/oxapay', [WebhookController::class, 'oxapay'])->name('webhook.oxapay');
 
+// Unified Payment System Routes
+require __DIR__.'/payment.php';
+
 require __DIR__.'/auth.php';
 
 Route::get('{slug}', Page::class)->where('slug', '.*')->name('page')->middleware(CheckPageSlug::class);