feat(Production): Complete production deployment infrastructure

- Add comprehensive health check system with multiple endpoints
- Add Prometheus metrics endpoint
- Add production logging configurations (5 strategies)
- Add complete deployment documentation suite:
  * QUICKSTART.md - 30-minute deployment guide
  * DEPLOYMENT_CHECKLIST.md - Printable verification checklist
  * DEPLOYMENT_WORKFLOW.md - Complete deployment lifecycle
  * PRODUCTION_DEPLOYMENT.md - Comprehensive technical reference
  * production-logging.md - Logging configuration guide
  * ANSIBLE_DEPLOYMENT.md - Infrastructure as Code automation
  * README.md - Navigation hub
  * DEPLOYMENT_SUMMARY.md - Executive summary
- Add deployment scripts and automation
- Add DEPLOYMENT_PLAN.md - Concrete plan for immediate deployment
- Update README with production-ready features

All production infrastructure is now complete and ready for deployment.

tests/debug/test-percentage-rollout.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+
+use App\Framework\FeatureFlags\FeatureFlag;
+use App\Framework\FeatureFlags\FeatureFlagContext;
+use App\Framework\FeatureFlags\FeatureFlagStatus;
+
+$flag = new FeatureFlag(
+    name: 'rollout-feature',
+    status: FeatureFlagStatus::CONDITIONAL,
+    conditions: ['percentage' => 50]
+);
+
+echo "Testing percentage rollout...\n";
+
+$enabledCount = 0;
+for ($userId = 1; $userId <= 10; $userId++) {
+    $context = (new FeatureFlagContext())->withUserId((string) $userId);
+    $enabled = $flag->isEnabledForContext($context);
+
+    echo "User ID {$userId}: " . ($enabled ? "ENABLED" : "DISABLED") . "\n";
+
+    if ($enabled) {
+        $enabledCount++;
+    }
+}
+
+echo "\nEnabled count: {$enabledCount} / 10\n";
+echo "Expected approximately 5 (50%)\n";