The merge conflict resolution during rebase incorrectly changed Requests.t
from a parameterized type to a monomorphic type:
- Before: type ('clock, 'net) t
- After (broken): type t

This broke all libraries that depend on requests (river, requests_json_api,
zotero-translation, zulip) as they expect the parameterized type to properly
abstract over Eio's clock and network types.

Restored these files from the original branch (324a64b):
- requests/lib/requests.ml
- requests/lib/requests.mli
- requests_json_api/lib/requests_json_api.ml
- requests_json_api/lib/requests_json_api.mli
- zotero-translation/zotero_translation.ml
- zotero-translation/zotero_translation.mli
- zulip/lib/zulip/lib/client.ml
- zulip/lib/zulip/lib/client.mli

River, requests, zulip, and all dependent libraries now build successfully.

The merge conflict resolution during rebase incorrectly removed:
- user_id and delivery_email optional parameters from User.create
- get_by_id function from Users module
- client accessor function from Bot_storage module

This commit restores the working version from the original branch (324a64b)
that was in place before the rebase started.

The core zulip library now builds successfully.