Document the `meta` query parameter

## Background

`content/guides/04.connect/3.query-parameters.md` documents every other query parameter (`fields`, `filter`, `search`, `sort`, `limit`, `offset`, `page`, `aggregate`, `groupBy`, `deep`, `alias`, `export`, `version`, `versionRaw`, `functions`, `backlink`) with its own `##` section, but `meta` has no section and isn't mentioned anywhere on the page or elsewhere in this repo.

`meta` was previously proposed for deprecation in favor of aggregation (directus/directus#15665), but that was closed as not planned in 2024 ("Not dropping it, it's too popular!"). It remains fully supported today.

## Scope

Add a `## Meta` section to `content/guides/04.connect/3.query-parameters.md`, following the existing section format (description, `::code-group` with REST/GraphQL/SDK tabs where applicable, any relevant `::callout`).

## Content notes

Source: `api/src/utils/sanitize-query.ts` (`sanitizeMeta`), `api/src/services/meta.ts` (`MetaService.getMetaForQuery`) in directus/directus.

- Accepts `total_count`, `filter_count`, a comma-separated combination of the two, or `*` for both.
- `total_count`: total number of items in the collection, ignoring any filters.
- `filter_count`: number of items matching the current filter/search.
- No GraphQL equivalent: GraphQL exposes counts through the separate `_aggregated` query type instead of a `meta` argument, so this section likely only needs REST + SDK tabs.

## Also noticed

The page's frontmatter `description` field lists `fields, filter, search, sort, limit, offset, page, aggregate, groupBy, deep, alias, and export` - missing `version`, `versionRaw`, `functions`, and `backlink` (which already have sections), as well as `meta`. Worth updating in the same PR since it's the same file.

Start with content/guides/04.connect/3.query-parameters.md and follow the existing query-parameter section format. Read sanitizeMeta in api/src/utils/sanitize-query.ts and MetaService.getMetaForQuery in api/src/services/meta.ts, then document the REST and SDK forms, explain the supported values, and note the GraphQL alternative. Update the frontmatter description to include all documented parameters, including meta.

Written by the indexing model from the issue text.