feat(monitoring): add Redis exporter + Sentry docs to deployment guide

- Add redis-exporter container to docker-compose (oliver006/redis_exporter, 32MB)
- Add Redis scrape target to Prometheus config
- Add 4 Redis alert rules: RedisDown, HighMemory, HighConnections, RejectedConnections
- Document Step 19b (Sentry Error Tracking) in Hetzner deployment guide
- Document Step 19c (Redis Monitoring) in Hetzner deployment guide
- Update resource budget and port reference tables

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/development/icons-guide.md

@@ -292,7 +292,7 @@ Add this script **before** Alpine.js in your HTML pages:
         <span>Options</span>
         <span x-html="$icon('chevron-down', 'w-4 h-4 ml-2')"></span>
     </button>
-    
+
     <div x-show="open" class="absolute right-0 mt-2 w-48 bg-white rounded-lg shadow-lg">
         <a href="#" class="flex items-center px-4 py-2 hover:bg-gray-100">
             <span x-html="$icon('edit', 'w-4 h-4 mr-2')"></span>
@@ -425,4 +425,4 @@ The icon system works in all modern browsers:
 
 - [Heroicons Official Site](https://heroicons.com/)
 - [Tailwind CSS Documentation](https://tailwindcss.com/docs)
-- [Alpine.js Magic Properties](https://alpinejs.dev/magics/el)
+- [Alpine.js Magic Properties](https://alpinejs.dev/magics/el)