Add boto3 dependency and update exercise/machine assets

- Added boto3 as a dependency in pyproject.toml and uv.lock.
- Introduced multiple new exercise images in various formats (jpg, webp, avif, png).
- Added new machine images to enhance the workout assets library.

services/bff/app/s3.py

@@ -10,6 +10,7 @@ ALLOWED_CONTENT_TYPES = {
     "image/jpeg": ".jpg",
     "image/png": ".png",
     "image/webp": ".webp",
+    "image/avif": ".avif",
 }