Better recovery after an interrupted recording

AirNote can now reconstruct the duration of an interrupted session from the readable audio before making it available for retry. It preserves valid saved time, excludes pauses and time outside the app, and leaves the surviving audio unchanged.

For supported remote sessions, AirNote can also reapply echo reduction before the recovered recording is transcribed. If that cannot be completed safely, AirNote keeps the raw fallback and flags the limitation for review.