fix: technical debts left by the Sites, Authors and SEO slices, plus backend support for the new Sites and Authors pagination

docs/api/articles.md

@@ -25,7 +25,7 @@ Visibility is unchanged: anonymous and unverified callers only see online articl
   "total": 30,
   "page": 1,
   "size": 25,
-  "counts": { "all": 30, "online": 30, "draft": 0 }
+  "counts": { "all": 30, "online": 30, "draft": 0, "suggestions": 4 }
 }
 ```
 
@@ -42,7 +42,7 @@ Visibility is unchanged: anonymous and unverified callers only see online articl
 - `items` is `[]` when empty, never `null`. Each item is the article object below.
 - Items follow `sort` (default `updated_at:desc`) across the whole list before paging. `title` ignores case, `status` orders on online state (`status:asc` puts drafts first), and every ordering ends with `id` descending so pages never overlap.
 - `total` is the number of visible articles matching `q` and `status`, before paging. `page` and `size` echo the values applied.
-- `counts` ignores `q` and `status`, so tab counts do not move while searching. For anonymous and unverified callers `all` equals `online` and `draft` is `0`, and `status=draft` answers `items: []` and `total: 0`.
+- `counts` ignores `q`, `status`, `site`, `seo`, `sort`, `page` and `size`, so tab counts do not move while searching. `suggestions` is the number of visible articles whose `seo_status` is `suggestions` (hidden and ready articles and dismissed codes are not counted); it equals the `total` of `?seo=suggestions` sent with no other filter by the same caller. For anonymous and unverified callers `all` equals `online` and `draft` is `0`, and `status=draft` answers `items: []` and `total: 0`.
 - Each item also carries `seo_status` and `seo_suggestions` (see [SEO status and suggestions](#seo-status-and-suggestions)). `seo` filters on the status before paging, so `total` follows it while `counts` do not.
 - A page beyond the last answers `200` with `items: []` and the real `total`.
 - An invalid `page`, `size`, `status`, `sort` or an over-long `q` answers `400` with the plain-text message `The request cannot be processed due to a mismatch in the format of the body.` An invalid `format` is reported first.