index: fix stuck Index webhook transfer notifications for webhook transcript-only deliveries

[ndom91]

Summary

• dismiss completed Index transfers that have no local recording entry
• prevents transcript-only webhook-only recordings from remaining as "Transferring recording" indefinitely

Verification

• git diff --check
• attempted ./gradlew :experimental:compileKotlinAndroid, but Gradle configuration cannot run in this workspace because ANDROID_HOME / local.properties is not configured

AI disclosure

AI was used to investigate the notification state flow and draft this focused fix. I reviewed the resulting change and understand that webhook-only transcript delivery intentionally has no local recording entry; a completed transfer is therefore terminal for its local notification.

[CLAassistant]

All committers have signed the CLA.