Improve the image optimization pipeline with better compression and
smarter variant generation:
- Change to_lossless_webp → to_optimized_webp (lossy, quality 90)
- Auto-resize uploads larger than 2000px to save storage
- Skip pre-generating JPEG variants (~50% disk savings)
- Add on-demand JPEG generation for legacy browsers (<5% of users)
- Add /images/:id/variant/:width route for dynamic serving
- Add VariantCache to supervision tree for startup validation
- Add image_cache to static paths for disk-based serving
The pipeline now stores smaller WebP sources and generates AVIF/WebP
variants upfront, with JPEG generated only when legacy browsers request it.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
