Fix string filter input focus "blink"; match other inputs

The string-criterion filter input (e.g. Playevent Note) had transition-all, so
on focus its border-color animated from the near-white default to the focus
blue — a visible white "blink". It also lacked an explicit border width and
focus:border-brand/ring-brand, so its focus came from the forms-plugin default.

Drop transition-all (the other inputs snap to focus), add border +
focus:border-brand focus:ring-brand, and use rounded-base — so it focuses
instantly to the same brand border as every other input.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

common/components/filters.py

@@ -1572,7 +1572,12 @@ def StringFilter(
         ("placeholder", placeholder),
         (
             "class",
-            "w-full rounded border-default-medium p-2 bg-neutral-secondary-medium text-body transition-all "
+            "w-full rounded-base border border-default-medium p-2 "
+            "bg-neutral-secondary-medium text-body "
+            "focus:border-brand focus:ring-brand "
+            # No transition-* here: with transition-all the border-color animated
+            # from near-white default → brand on focus, which read as a white
+            # "blink". The other inputs snap to the focus state, so this does too.
             + ("opacity-50 cursor-not-allowed" if input_disabled else ""),
         ),
     ]