fix(review): address CodeRabbit feedback

- swap direct i18next t imports for the useTranslation hook so the four
  touched components re-render on language change
- localize the buffer seconds unit via a buffer_seconds key instead of a
  literal trailing s
- reword the useAppRouter guard comment to match its real scope

components/video-player/controls/TechnicalInfoOverlay.tsx

@@ -344,8 +344,9 @@ export const TechnicalInfoOverlay: FC<TechnicalInfoOverlayProps> = memo(
           )}
           {info?.cacheSeconds !== undefined && (
             <Text style={textStyle}>
-              {t("player.technical_info.buffer")} {info.cacheSeconds.toFixed(1)}
-              s
+              {t("player.technical_info.buffer_seconds", {
+                seconds: info.cacheSeconds.toFixed(1),
+              })}
             </Text>
           )}
           {info?.voDriver && (