Refactor episode regex handling for improved clarity and maintainability

Updated the separator handling in the buildEpisodeRegex function to enhance readability. The change replaces the inline conditional for the gap with a dedicated variable, making the code more understandable while maintaining functionality.

frontend/src/features/admin/media/episode-regex.ts

@@ -56,7 +56,8 @@ export function buildEpisodeRegex(fileName: string, occurrenceIndex: number): st
   // к первому сезону, и на «S02E05» оно бы уже не сработало.
   const anchor = trailingRun(anchorSource, isLetter)
 
-  if (anchor) return `${escapeRegex(anchor)}${gap ? String.raw`[\s._-]*` : ''}${digits}`
+  const separator = gap ? String.raw`[\s._-]*` : ''
+  if (anchor) return `${escapeRegex(anchor)}${separator}${digits}`
 
   // Слова перед числом нет — цепляемся за последний разделитель («- 05», «(05)»).
   const punctuation = gap.trim().slice(-1)