ui: move get_datetime tool to frontend (#27255)

* ui: move get_datetime tool to frontend

* clarify docs

* server: drop the now unused ctime include

strftime() and gmtime_r() were the only users, both went away with the
get_datetime tool. Also make the renderer's catch inert: the browser
executor always emits JSON, so a non-JSON result is no longer a date to
display.

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Co-authored-by: Pascal <admin@serveurperso.com>

tools/ui/src/lib/constants/index.ts

@@ -59,4 +59,5 @@ export * from './uri-template.constants';
 export * from './url.constants';
 export * from './working-directory.constants';
 export * from './read-media';
+export * from './get-datetime';
 export * from './browser-info';