refactor(serverlibrary): move suffixes to library

move audio/video suffixes to serverlibrary
remove from audiobooks_library, ffmpeg_handling

media_editing/ffmpeg_handling.py

@@ -23,9 +23,6 @@ from serverlibrary import *
 logging.setLoggerClass(CustomLogger)
 logger: CustomLogger = logging.getLogger(__name__)  # type: ignore[assignment]
 
-VIDEO_EXTS = {".mp4", ".mkv", ".avi", ".mov", ".webm"}
-AUDIO_EXTS = {".mp3", ".m4a", ".m4b", ".opus"}
-
 # ----------------------------
 # OUTPUT ENFORCEMENT (clean + centralized)
 # ----------------------------