feat: add media upload pipeline with multipart support, blurhash generation, and R2 storage

- Add project_media table with image/video variants, ordering, and metadata
- Implement multipart upload handlers with 50MB limit
- Generate blurhash placeholders and resize images to thumb/medium/full variants
- Update ProjectCard to use media carousel instead of mock gradients
- Add MediaManager component for drag-drop upload and reordering

src/main.rs

@@ -12,6 +12,7 @@ mod github;
 mod handlers;
 mod health;
 mod http;
+mod media_processing;
 mod middleware;
 mod og;
 mod proxy;