refactor: move waveform guard to flag definition for consistency

Use typeof === 'undefined' check in the flag definition (line 242),
matching the established pattern for seconds (line 239) and
jpegThumbnail (line 241), instead of truthy check at usage point.

This is more precise: typeof distinguishes undefined (not provided)
from null (explicitly passed), and keeps all three media-processing
flags using the same guard pattern.

Co-Authored-By: Renato Alcara

src/Utils/messages.ts

@@ -239,7 +239,7 @@ export const prepareWAMessageMedia = async (
 	const requiresDurationComputation = mediaType === 'audio' && typeof uploadData.seconds === 'undefined'
 	const requiresThumbnailComputation =
 		(mediaType === 'image' || mediaType === 'video') && typeof uploadData['jpegThumbnail'] === 'undefined'
-	const requiresWaveformProcessing = mediaType === 'audio' && uploadData.ptt === true
+	const requiresWaveformProcessing = mediaType === 'audio' && uploadData.ptt === true && typeof uploadData.waveform === 'undefined'
 	const requiresAudioBackground = options.backgroundColor && mediaType === 'audio' && uploadData.ptt === true
 	const requiresOriginalForSomeProcessing = requiresDurationComputation || requiresThumbnailComputation
 	const { mediaKey, encFilePath, originalFilePath, fileEncSha256, fileSha256, fileLength } = await encryptedStream(
@@ -297,7 +297,7 @@ export const prepareWAMessageMedia = async (
 					logger?.debug('computed audio duration')
 				}
 
-				if (requiresWaveformProcessing) {
+				if (requiresWaveformProcessing && !uploadData.waveform) {
 					uploadData.waveform = await getAudioWaveform(filePath, logger)
 					logger?.debug('processed waveform')
 				}