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

tests/Feature/Unit/ProviderRegistryTest.php

@@ -0,0 +1,77 @@
+<?php
+
+use App\Services\Payments\ProviderRegistry;
+use App\Services\Payments\Providers\StripeProvider;
+
+test('can register payment provider', function () {
+    $registry = new ProviderRegistry;
+    $provider = new StripeProvider;
+
+    $registry->register('stripe', $provider);
+
+    expect($registry->has('stripe'))->toBeTrue();
+    expect($registry->get('stripe'))->toBe($provider);
+});
+
+test('can get all providers', function () {
+    $registry = new ProviderRegistry;
+    $stripeProvider = new StripeProvider;
+
+    $registry->register('stripe', $stripeProvider);
+
+    $providers = $registry->getAllProviders();
+
+    expect($providers)->toHaveCount(1);
+    expect($providers->get('stripe'))->toBe($stripeProvider);
+});
+
+test('can get active providers only', function () {
+    $registry = new ProviderRegistry;
+    $stripeProvider = new StripeProvider;
+
+    $registry->register('stripe', $stripeProvider);
+
+    $activeProviders = $registry->getActiveProviders();
+
+    expect($activeProviders)->toHaveCount(0); // Stripe is inactive without API key
+});
+
+test('can unregister provider', function () {
+    $registry = new ProviderRegistry;
+    $provider = new StripeProvider;
+
+    $registry->register('stripe', $provider);
+    expect($registry->has('stripe'))->toBeTrue();
+
+    $result = $registry->unregister('stripe');
+    expect($result)->toBeTrue();
+    expect($registry->has('stripe'))->toBeFalse();
+});
+
+test('can validate providers', function () {
+    $registry = new ProviderRegistry;
+    $stripeProvider = new StripeProvider;
+
+    $registry->register('stripe', $stripeProvider);
+
+    $results = $registry->validateProviders();
+
+    expect($results)->toHaveKey('stripe');
+    expect($results['stripe']['active'])->toBeFalse();
+    expect($results['stripe']['supports_recurring'])->toBeTrue();
+    expect($results['stripe']['supports_one_time'])->toBeTrue();
+});
+
+test('can get provider statistics', function () {
+    $registry = new ProviderRegistry;
+    $stripeProvider = new StripeProvider;
+
+    $registry->register('stripe', $stripeProvider);
+
+    $stats = $registry->getProviderStats();
+
+    expect($stats['total_providers'])->toBe(1);
+    expect($stats['active_providers'])->toBe(0);
+    expect($stats['recurring_providers'])->toBe(0);
+    expect($stats['one_time_providers'])->toBe(0);
+});