Add server row sorting, filtering, and search

[priethor]

What

Closes #102.

Moves common collection row queries onto GET /cortext/v1/rows: sorting, field filters, grouped filters, and split-term search. The server now handles the field types we can query reliably, while unsupported query shapes stay on the client instead of being silently sent to the endpoint.

Why

The table already fetched rows from the rows endpoint, but search and richer filters still depended on client-side behavior. This adds server query support for the normal database-table cases without taking on server pagination changes in this PR.

How

Server-supported fields:

Field	Sort	Filter	Search
Title	Yes	Yes	Yes
Text	Yes	Yes	Yes
Email	Yes	Yes	Yes
URL	Yes	Yes	Yes
Number	Yes	Yes	No
Date	Yes	Yes	No
Datetime	Yes	Yes	No
Select	Yes, by stored value	Yes	No
Multiselect	No	Yes	No
Checkbox	Yes	Yes	No
Created / Last edited	Yes	No	No
Created by / Last edited by	No	No	No
Relation	No	No	No
Rollup	No	No	No

• Uses a local field capability map until WordPress or DataViews exposes a capability contract for custom field types.
• Compiles supported filters through RowsFilterQuery and a small WP_Meta_Query extension for comparison shapes WP core does not support yet.
• Sends only server-safe DataViews query state, with client fallback when a view contains unsupported query parts.
• Leaves select sorting as stored-value sorting for now, not curated option order.

Testing Instructions

1. Create a collection with title, text, number, date, datetime, select, multiselect, checkbox, email, URL, relation, and rollup fields.
2. Sort by title, text, number, date, datetime, select, checkbox, and URL. Check that supported fields sort correctly.
3. Add filters for title/text/email/URL contains, number greater than, date before, select is one of, multiselect contains, and checkbox checked. Check that visible rows match.
4. Search for two words where one is in the title and the other is in a text-like field. Check that the row stays visible.
5. Try sorting or filtering relation and rollup fields. They should not be treated as server-supported fields.

Screen recording

Grabacion.de.pantalla.2026-05-13.a.las.16.57.16.mov