fix: detect view-once media (image/video/audio) (#309)

* fix: detect view-once media (image/video/audio) on stanza 1 for linked devices

When a view-once arrives at a linked device (InfiniteAPI), the server sends:
- Stanza 1: enc payload with full media metadata (mediaKey, directPath) wrapped in
  viewOnceMessage > imageMessage/videoMessage/audioMessage with viewOnce: true
- Stanza 2: unavailable view_once fanout placeholder (already handled)

Previously only stanza 2 set key.isViewOnce = true. Stanza 1 was emitted as
plain media with no view-once indicator, making it indistinguishable from regular
media on the consumer side (messages.upsert).

This fix inspects the decrypted proto for viewOnceMessage (v1/v2/v2Ext) wrappers
containing a media message with viewOnce=true and propagates key.isViewOnce=true.

The viewOnceMessage wrapper is also used for interactive messages (carousel,
buttons, lists) but those carry interactiveMessage/listMessage inside -- never
imageMessage.viewOnce / videoMessage.viewOnce / audioMessage.viewOnce.
The distinction is unambiguous and does not affect interactive message handling.

Verified via WA Desktop

src/Utils/decode-wa-message.ts

@@ -392,6 +392,23 @@ export const decryptMessageNode = (
 						} else {
 							fullMessage.message = msg
 						}
+
+						// Detect view-once media on stanza 1 received by linked device.
+						// viewOnceMessage wrapper is also used for interactive messages
+						// (interactiveMessage, listMessage, nativeFlowMessage) -- those do NOT have
+						// imageMessage.viewOnce / videoMessage.viewOnce / audioMessage.viewOnce = true.
+						// Only real view-once media carries viewOnce: true on the inner media message.
+						const viewOnceInner =
+							msg.viewOnceMessage?.message ||
+							msg.viewOnceMessageV2?.message ||
+							msg.viewOnceMessageV2Extension?.message
+						if (
+							viewOnceInner?.imageMessage?.viewOnce ||
+							viewOnceInner?.videoMessage?.viewOnce ||
+							viewOnceInner?.audioMessage?.viewOnce
+						) {
+							fullMessage.key.isViewOnce = true
+						}
 					} catch (err: any) {
 						// Check if this is a final failure after all retries exhausted
 						const isRetryExhausted = err instanceof RetryExhaustedError