Allow text selection on checkbox labels (#36970)

Remove `user-select: none` from checkbox labels to allow text selection
which is sometimes useful.

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Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>

web_src/css/modules/checkbox.css

@@ -101,7 +101,6 @@ input[type="checkbox"]:indeterminate::before {
   cursor: auto;
   position: relative;
   display: block;
-  user-select: none;
 }
 
 .ui.checkbox label,