SOLR-18460: Ensure all curl commands follow the same pattern

[serhiy-bzhezytskyy]

https://issues.apache.org/jira/browse/SOLR-18460

Description

Curl examples across the ref guide were inconsistent: some put the URL after the headers/body instead of right after curl, most kept -X POST alongside -d/--data/--data-binary (redundant, since curl already switches to POST when a body is given), and many started with a $ shell-prompt character that breaks a direct copy-paste.

Solution

Reordered every affected curl example to curl 'URL' -H '...' -d '...' (or the multi-line equivalent for larger JSON bodies), dropped -X POST wherever a body already implies it, and stripped the leading $ from curl lines. Left -X POST in place where there's no body at all (curl defaults to GET and needs the override) and on the one --upload-file/-T example (that flag makes curl default to PUT, not POST, so removing -X POST there would silently change the request).

44 files, all under solr/solr-ref-guide/modules/*/pages/.

Tests

Ran ./gradlew :solr:solr-ref-guide:buildLocalAntoraSite and :checkSiteLinks before and after: same 6 pre-existing warnings (unrelated, tracked in #4922/SOLR-18464), no new ones, no broken links. Re-grepped the whole ref guide for the three rule clauses after the change: 0 remaining curl … -X POST … (-d|--data) combinations, 0 remaining ^$ curl lines.

AI-assisted (Claude Sonnet 5).

[serhiy-bzhezytskyy]

@epugh tagging you since this is under SOLR-18459/SOLR-18460, which you filed.

[epugh]

This LGTM! I'm going to ping Jan and David as they may have opinons on the overall structure we chose, but the mechanics of this look great. I like all the clean ups.