Pass request params as args in 6 helpers (FastAPI prep)

## Problem / Opportunity

Handlers read request data with `web.input()`. Helpers also call `web.input()` deep in the code. This hidden global blocks FastAPI migration. FastAPI needs explicit params.

This issue tracks 6 helpers. Each helper must take explicit args. Handlers must pass the args down. This work makes later FastAPI conversion easy. It changes no behavior.

Audience: developers who migrate web.py handlers to FastAPI.

## Proposal

Change 6 helpers. Remove `web.input()` from each helper. Update callers to pass values. Keep behavior identical. Do not add new tests. Run existing tests only.

Tracked in 3 sub-issues (one PR each), linked below.

### Group 1 — Trivial prefs (no risk)

* `openlibrary/book_providers.py:756` `get_provider_order()` — read `?providerPref` in handler. Pass `provider_pref` as arg.
* `openlibrary/plugins/upstream/utils.py:1431` `get_ia_host()` — read `?dev_host` in handler. Pass `dev_host` as arg.
* `openlibrary/plugins/worksearch/code.py:321` `get_remembered_layout()` — read `?layout` and cookie in handler. Pass both as args.

### Group 2 — Security paths (needs care)

* `openlibrary/plugins/upstream/spamcheck.py:35` `is_spam()` — require `i` from caller. Remove `web.input()` fallback.
* `openlibrary/plugins/recaptcha/recaptcha.py:34` `validate()` — pass `g-recaptcha-response` and client IP as args. Keep `web.form.Validator` shim for web.py.

### Group 3 — High-traffic page

* `openlibrary/plugins/upstream/models.py:483` `Author.get_books()` — read `sort`, `page`, `rows`, `mode` in handler. Pass all 4 as args. Update `openlibrary/templates/type/author/view.html:23`.

## Breakdown

Implementation details for maintainers.

#### Related files

* `openlibrary/book_providers.py`
* `openlibrary/plugins/upstream/utils.py`
* `openlibrary/plugins/worksearch/code.py`
* `openlibrary/plugins/upstream/spamcheck.py`
* `openlibrary/plugins/recaptcha/recaptcha.py`
* `openlibrary/plugins/upstream/models.py`
* `openlibrary/templates/type/author/view.html`
* `openlibrary/templates/site/donation_banner.html`
* `openlibrary/templates/account/ia_thirdparty_logins.html`

Out of scope: `ListRecord.from_input()` (`openlibrary/plugins/openlibrary/lists.py:135`), framework processors, `changequery`, middleware, templates/macros port, coverstore. File that separately.

#### Requirements Checklist

* [ ] Group 1 done: 3 helpers take explicit args. No `web.input()` inside. Callers updated.
* [ ] Group 2 done: `is_spam` requires `i`. `validate` takes response and IP. Callers updated.
* [ ] Group 3 done: `get_books` takes `sort`, `page`, `rows`, `mode`. Template updated.
* [ ] No behavior change in any group.
* [ ] Existing tests pass (`make test-py-uv`). Do not add new tests.
* [x] 3 sub-issues exist: #13537, #13538, #13539. Each links to this epic.

#### Stakeholders

Lead: @RayBB.

Start with sub-issues #13537, #13538, and #13539 rather than taking this epic as one change. Read the six listed helper locations and their callers, then run `make test-py-uv`; done means each helper receives explicit request values, the author template is updated, and existing behavior and tests remain unchanged.

Written by the indexing model from the issue text.