Avatar and account logo rendering fails with S3-backed Active Storage

## Summary

When `ACTIVE_STORAGE_SERVICE` is set to `s3`, custom user avatars and account logos upload successfully but fail to render afterward.

This happens because the controllers call `ActiveStorage::Blob.service.path_for(...)`, which works for `DiskService` but raises on `ActiveStorage::Service::S3Service`.

## Reproduction

1. Configure Campfire production storage to use `ACTIVE_STORAGE_SERVICE=s3`.
2. Point it at any S3-compatible backend.
- I reproduced this with MinIO, but this should affect any `ActiveStorage::Service::S3Service` backend.
3. Upload a user avatar from `/users/me/profile`.
4. Optionally upload an account logo as well.

## Expected

The uploaded avatar/logo should render normally.

## Actual

The upload succeeds, but the follow-up image request returns `500` and the UI shows a broken image.

## Error

```ruby
NoMethodError (undefined method 'path_for' for an instance of ActiveStorage::Service::S3Service)
```

Affected code paths on `main`:

- `app/controllers/users/avatars_controller.rb`
- `app/controllers/accounts/logos_controller.rb`

## Notes

In my reproduction, the blob upload and subsequent download both succeeded. The failure happens only when the controller tries to serve the processed variant back using the disk-only `path_for` API.

The fix was to stream the processed representation through Active Storage instead of reading it via `path_for`.

Start with app/controllers/users/avatars_controller.rb and app/controllers/accounts/logos_controller.rb, tracing how each serves the processed representation after upload. Reproduce with ACTIVE_STORAGE_SERVICE=s3 against an S3-compatible backend such as MinIO; done means uploaded avatars and account logos render without the path_for error and the follow-up image request no longer returns 500.

Written by the indexing model from the issue text.