feat: add capacity planning docs, image upload system, and platform health monitoring

Documentation:
- Add comprehensive capacity planning guide (docs/architecture/capacity-planning.md)
- Add operations docs: platform-health, capacity-monitoring, image-storage
- Link pricing strategy to capacity planning documentation
- Update mkdocs.yml with new Operations section

Image Upload System:
- Add ImageService with WebP conversion and sharded directory structure
- Generate multiple size variants (original, 800px, 200px)
- Add storage stats endpoint for monitoring
- Add Pillow dependency for image processing

Platform Health Monitoring:
- Add /admin/platform-health page with real-time metrics
- Show CPU, memory, disk usage with progress bars
- Display capacity thresholds with status indicators
- Generate scaling recommendations automatically
- Determine infrastructure tier based on usage
- Add psutil dependency for system metrics

Admin UI:
- Add Capacity Monitor to Platform Health section in sidebar
- Create platform-health.html template with stats cards
- Create platform-health.js for Alpine.js state management

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/marketing/pricing.md

@@ -6,6 +6,8 @@
 
 A focused Order Management System built specifically for Luxembourg e-commerce. Works alongside Letzshop, not instead of it. Provides the operational tools Letzshop lacks: real inventory, correct invoicing, customer ownership.
 
+> **Infrastructure Planning:** See [Capacity Planning](../architecture/capacity-planning.md) for resource requirements, server sizing, and scaling guidelines per tier.
+
 ---
 
 ## Market Context