refactor(i18n): ask the catalogue for a sentence in one helper

`t()` answers a missing key with the key, so "does this code have a
sentence" was a comparison written inline at every site that wanted a
code's sentence or a fallback, twenty-odd times in several spellings.
translateOrNull, translateCodeOrNull and translateCode in
src/lib/i18n/translate-code.ts now hold that probe, every site uses
them, and a guard refuses the inline comparison anywhere else.

src/app/insights/workouts/page-client.tsx

@@ -19,6 +19,7 @@ import { useAuth } from "@/hooks/use-auth";
 import { useRecordCapabilities } from "@/hooks/use-record-capabilities";
 import { canLogWorkout } from "@/lib/workouts/manual-entry";
 import { QueryErrorCard } from "@/components/ui/query-error-card";
+import { translateOrNull } from "@/lib/i18n/translate-code";
 
 /**
  * v1.4.32 — `/insights/workouts`.
@@ -82,9 +83,7 @@ export default function InsightsWorkoutsPageClient() {
   const sportLabel = (sport: string) => {
     // A sport enum the bundle has no copy for renders as its canonical
     // string rather than a raw key — same fallback the list rows use.
-    const key = `insights.workouts.sport.${sport}`;
-    const label = t(key);
-    return label === key ? sport : label;
+    return translateOrNull(t, `insights.workouts.sport.${sport}`) ?? sport;
   };
 
   return (