fix: validate uploaded media files

tests/test_uploads_repository.py

@@ -6,6 +6,12 @@ from zyrarbot.storage.uploads_repository import UploadsRepository
 
 
 class UploadsRepositoryTest(unittest.TestCase):
+    def test_only_audio_and_video_extensions_are_supported(self):
+        self.assertTrue(UploadsRepository.is_supported_filename("song.MP3"))
+        self.assertTrue(UploadsRepository.is_supported_filename("video.webm"))
+        self.assertFalse(UploadsRepository.is_supported_filename("program.exe"))
+        self.assertFalse(UploadsRepository.is_supported_filename("document.pdf"))
+
     def test_legacy_root_files_are_assigned_to_first_guild(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)